A Year of Teaching Swift

We are nearly at the end of the school year here in Scotland and I wanted to take some time to reflect on the experience of teaching the Computer Science curriculum this year using Swift Playgrounds and Apple's Learn to Code curriculum.


One of the projects I have been engaged with over the past few years is to move our Computer Science teaching out of the senior years and into the earlier years of secondary school. I'm not done with this yet but we are getting there.

In 2016/17, I taught the following courses:

  • Primary 7 (6th grade) - Introduction to Computational Thinking using Pixar in a Box
  • Primary 7 (6th grade) - Introduction to Computer Programming with Hopscotch
  • Secondary 1 (7th grade) - Learn to Code 1 & 2
  • Secondary 2 (8th grade) - Learn to Code 1 & 2

I taught the same course to S1 and S2 this year because we were still making the transition and this class hadn't done it before. In general, we obviously wouldn't teach the same course two years in a row.

I want to review the experience of teaching Learn to Code 1 and 2 here. Pixar in a Box is another post for another time but the idea with that is to promote the ideas of Computational Thinking without necessarily going straight to code.

Learn to Code

In the Learn to Code curriculum, there are three books called Learn to Code 1, 2 and 3 which use the Swift Playgrounds app as their learning tool. There are also two earlier books called Get Started with Code 1 and 2 which use either Tynker or Codespark Academy, and two later books called Introduction to App Development with Swift and App Development with Swift. These later two books use Xcode and macOS and extend up into college years. I'm only going to focus on the Learn to Code books here.

Learn to Code 1 and 2 were introduced alongside Swift Playgrounds at WWDC 2016. I started teaching them in October 2016, just after iOS 10 shipped.

Course Structure

The structure of the two books are really of a piece. Together, they provide a curriculum that covers much of the basics of a Computer Programming curriculum: commands, functions, loops, conditionals, variables, constants, arrays and basic object oriented programming.

In general, I think that the books introduce most of the concepts in an accessible way and do a good job of providing a staged progression through each of the topics.

Both classes that I taught Swift to this year had one term's prior experience in programming with Hopscotch and had also been through the Introduction to Computational Thinking class.

The Learn to Code World

Each of the books provide a series of exercises in each chapter that introduce and progressively challenge the skills that students are supposed to be learning at that point.

The format is nearly always the same: there is a character in a 3D puzzle world and the student is required to write code to "solve" the puzzle - however that is defined in the specific challenge.

In the world, there are collectible gems, toggle-able switches, moveable platforms and portals that transport you to other parts of the map. All of these make for quite an engaging game-like world and provide enough variety that the challenges rarely seem repetitive.

One issue I have with the constant use of a 3D map based approach is that, in my experience, it does disadvantage students who are not as strong in spatial reasoning and to some extent advantages students who are strong in that area but may not be as good at abstract reasoning as others.

Swift as a Teaching Language

I have taught a range of programming languages over the years. Primarily Visual Basic, Ruby and Python. I liked Ruby the best so far and hated Python for its crazily inconsistent library programming.

Swift is the closest thing to Ruby I've used. It is very consistent and predictable in its syntax and mostly makes sense as you read it. My only actual bugbear in the syntax that you explore in Learn to Code 1 and 2 is that the use of let to declare a constant isn't as intuitively obvious to students as var is.

Swift is a pretty decent teaching language at this level. It doesn't require much in the way of obscure ceremony or boilerplate code. I've seen students really start to bend the syntax to their will in some of the later exercises and this is really pleasing to see.

The Student Experience

From observation and talking with students during the class, I observed a few significant differences from any previous programming curriculum that we had used.

In times past the experience was that, if you were an able student in Computing, you would get your programs working. If you were not an able student, your experience would be almost insurmountable challenges to get anything working. Working or not-working was the differentiator in the class.

In the Learn to Code curriculum, I found that everyone got something working. The difference between the stronger students and the weaker students then was more to do with evaluations of the complexity of their solution, the understandability and style of their solutions or other factors like memory and time efficiency.

I have never really had these kinds of conversations in classes at this level before. It has been an incredibly satisfying year to get the opportunity to debate which of three possible solutions is the 'best' for a given problem and, further, what definition of 'best' we should accept.

For example, we looked at some solutions where students had written extremely compact code. It became a bit of a competition in the class to see who could solve a problem with the least code. Of course, this is almost never a desirable metric in practice, so I spent quite a lot of time teaching about Brian Kernighan's maxim:

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.

I can't point to many areas of the course that students found overwhelmingly difficult. The course is well-paced with enough practice on each technique that students can consolidate their learning. The later section in Learn to Code 2 in which Arrays are introduced could use a slightly shallower learning curve, but it wasn't too difficult overall.

The Teacher Experience

Apple provides a teacher guide for all of their courses. In the early days I kept to that guide quite closely but as the term wore on and I gained more confidence in the material, I felt freer to move away from that document. This was good and bad. Some of the things in the teacher guide I was kind of uncomfortable doing in class - there's one chapter that asks you to lead the class in dancing and that is simply not going to happen. At other times, though, I think I could have delivered a better class if I had used their lesson starters instead of my own.

Apple's teacher guides also encourage you to use Seesaw to gather evidence of the students' work. I quickly abandoned this practice as the sheer volume of material produced was quickly overwhelming. Between screenshots and code exercises, my class of 12 could easily produce 50-60 individual items that I was supposed to look at and approve in Seesaw in one class hour.

Instead, I took the approach of simply being far more active in the classroom. Instead of silent work for an hour and then offline grading, I asked the students to show me their solutions as they completed them and we would have conversations about the success or failure of their solutions live in class. This was, in some ways, much harder and more active work for me but it meant that I got to have those qualitative conversations about code that I had been looking for for so long.


What Learn to Code 1 and 2 rather lack is any way to formally evaluate a student's learning. A rubric is supplied, which I used, but there are no tests as such and no homework exercises. I ended up designing my own end-of-year test for Learn to Code and used the results of that test alongside the Learn to Code rubric to report to parents.

During the year, I also designed a series of weekly homework exercises based on Learn to Code 1 and tested them with the students going through the class this year (their results were not formally recorded as grades).

I have always found it difficult to set homework in computer programming classes because there is so little support available at home in this area that students can have wildly varying results. Instead, what I have done, is focus on code comprehension rather than code writing in exercises that will go home. I don't ask students to write code outside of class but to read code that I have written and either debug it or describe its behaviour. I'm in the early stages of doing this but I think this is a more sensible approach to programming exercises without teacher support.


Teaching Learn to Code 1 and 2 took me about 60 class hours over the course of this school year. I think this would have been slightly longer if I had stuck more rigidly to the Apple teacher guides and gone through all the exercises before letting the students code.

On reflection, I think that covering both Learn to Code 1 and 2 was maybe just a little too much for one school year. The learning went very well overall but both I and the pupils were somewhat running out of steam by the end of LtC 2 and I think we were all glad to finish when we did.

Future Improvements

I am definitely going to continue teaching Swift at school. As we go forward, I think a few improvements could be made.

Firstly, I would like Apple to publish a road map for future Learn to Code books. When I started planning the year, Learn to Code 1 and 2 were the only books in existence and we didn't know that there would ever be a Learn to Code 3 until the day it shipped. We plan learning experiences over the long run and it would be very helpful to know what's coming - or even if nothing else is coming.

I don't think many changes are needed in the Learn to Code 1 and 2 course itself. I'm looking forward to teaching it again. However, the aforementioned lack of summative assessment is something that would be worth looking at.

I would like to see a Learn to Code 4/5 where some iOS APIs are introduced within Swift Playgrounds. SceneKit and MapKit might be good candidates for "fun" APIs but I'm also interested in using lower-level network programming to teach about the structure of the internet.pl

The Swift Playgrounds app has worked well for us in general but a few things could help:

  • I would like to see a "teacher screen" mode where the code is much larger for the students to see.
  • Power efficiency was an issue at some points during the year but recent updates to the app have improved that significantly.
  • Some ability to transfer individual solutions between devices without having to transfer the entire book would be welcome. Sometimes you need to give a student a complete or partial solution for various reasons.
  • The ability to extract an individual page of a Playgrounds book would be convenient. Sometimes you want to use individual exercises by themselves.
  • You currently can't reset the in-book world to its initial state without re-running the program.
  • More debugging options would be helpful, such as breakpoints and variable inspectors.
  • When the books get updated, a detailed explanation of what changed and why would help. It's weird when your 'textbook' changes out from under you.
  • Integration with Apple Classroom to be able to open students directly into a particular exercise.

Overall, teaching Swift has been a pleasure this year and I look forward to doing more!

Theft and Loss Recovery for iOS Users

Recently, I took my family on a trip to France. We had a wonderful time but it was slightly marred by the events of the last evening in Paris when one of our bags was stolen from literally at our feet in a restaurant.

A number of things were lost but the most concerning one was my wife's iPhone. We were able to quickly disable her bank cards and her SIM card, so nothing serious was lost, except photographs, but the incident got me thinking about what I would do if my own devices were lost in this way.

Fortunately, the bag was stolen on the final day of the trip and not the first, otherwise we would have had serious problems throughout the holiday. This is another post for another time, but it's kind of shocking how crippling the loss of a phone is.

Certainly, the loss of the devices themselves is not trivial but the bigger concerns are (a) how to protect the data that is on those devices or accessible through them and (b) how to get back into my accounts and data in order to continue my trip.

My Typical Setup

I use iOS devices and I use 1Password religiously. Every account I have is stored in 1Password and I have memorised none of those passwords. I recently changed my Apple ID password to an unmemorable password (a mistake, as we shall see later), so the only password I have memorised is the one to unlock 1Password.

I use 1Password for Families, so my data is hosted by 1Password itself. I have 2-factor authentication turned on for every account that supports it, including my Apple ID, personal and work Google accounts, Dropbox, Evernote and others.

All my devices have passcodes. I use alphanumeric passcodes on my iOS devices. I have Touch ID enabled. My Apple Watch locks when I take it off. Find My iPhone is turned on for all devices and Activation Lock is enabled.

I'm really doing my best here. Ironically, though, it's this good level of security that makes the recovery trickier.

My Disaster Scenario

Fortunately for us, only one device was lost in the random snatch of a single bag. For this post, though, I'm going to assume the absolute worst case scenario and, if I can work back from that, I can work back from anything less bad than that.

Let's say, for the sake of argument, that I'm walking down the street in a large city somewhere abroad and I'm approached and forcibly relieved of all the valuable possessions on my person. In a typical tech conference scenario, that would be my iPhone, iPad and Apple Watch all gone.

What now? Well, there are two phases to this: damage limitation and disaster recovery.

Damage Limitation

The first concern is to limit the exposure of my data to attackers and Find My iPhone is the first place to go here.

Find My iPhone can be accessed through an app on another iOS device or on the web. Sensibly, you don't need to go through 2-factor authentication to get to this - I mean, you've just lost one of those factors - so you just need your iCloud password.

Here was my first problem: I don't know my iCloud password. It's long, it's random and it's stored in 1Password. So now I have to get into 1Password, just to send an erase command to my devices.

For me, that would take too long so my first task in this security audit is to change my password to something complex and long but still memorable without support.

Assuming I can get into Find My iPhone, the next thing I would do is put all my devices into Lost Mode. Lost Mode does a number of things but most importantly it disconnects any bank cards you have in Apple Pay from being used through any device in Lost Mode.

Lost Mode is actually better than immediately sending a remote wipe to your device. A wipe requires the device to be online to receive the command but Lost Mode will kill your Apple Pay in Apple's payment processing back end so you are immediately protected whether or not the device is online.

If you can see the device, then you might be in good shape to try and get it back. Many criminals, however, know to either turn off the iPhone or remove the SIM card, so it goes dark immediately. In my opinion, iOS devices should have locking SIM trays and require a password to shut down the device to close this loophole.

A point about getting devices back: I do not recommend you just follow the map and try and find your device. Instead, hand this information over to law enforcement and let them chase the bad guys.

Disaster Recovery - iCloud

So, assuming the worst happens and all your devices are gone forever - what now? Well, I need to get back into those accounts.

Let's assume that somehow I can acquire a new device. As a side issue, ask yourself how you would even do that. If everything was gone - how would you call home? How would you get money? Do you even have those numbers written down anywhere that isn't in your phone?

Also bear in mind that to activate an iPhone you might also need a working SIM card. I'm not sure if this is true everywhere on all networks, but I've certainly seen that requirement in the UK.

To sign into a new device, you need your iCloud password and a way to access your 2-factor information. With Apple's current implementation of 2-factor authentication, you can use a number of methods to get that second factor.

First, you can get it from another trusted device. This is when that dialog pops up and tells you that someone is trying to log in from a specific location, you tap OK and then you see a 6-digit code that you can provide.

Except in this scenario, all your trusted devices are gone. So that's out.

The next thing you can do is have a code sent to a trusted phone number. But your phone is gone and the SIM card is gone with it, so no calls or texts to that number.

Here, I discovered the second flaw in my setup. I only had my own devices set up as Trusted Devices and I only had one phone number set up as a Trusted Number - namely, my iPhone's phone number.

So, second task in this security audit: register a few other Trusted Numbers with Apple, and make sure that at least one of them is someone that you're not travelling with. Additionally, make sure you know how to get in touch with that person without access to any devices or iMessage or any social media.

It's also worth noting that, unlike most 2-factor authentication schemes, Apple no longer provides a "recovery key". Recovery keys for 2-factor authentication are like "safety net" keys that you can enter instead of getting a 2-factor authentication code from any of the usual channels. Google, Dropbox, et al. provide these kind of keys but Apple does not. Your only options are Trusted Devices, Trusted Phone Numbers or talking to Apple Support about getting back into your account.

Disaster Recovery - 1Password

The last thing I need to do to get back up and running is to get into my 1Password database. I'm using 1Password for Families and I do know my 1Password master password. However, that's not enough to get into 1Password.

1Password requires two pieces of information to get in: the master password and the account's Secret Key. When you are using 1Password for Families or Teams, you can create what is called a 1Password Emergency Kit. This is a PDF that contains your 1Password Secret Key and your login information (but not your password). I wasn't carrying this, but I had it stored in ... a place that I couldn't get to without access to 1Password!

So, third to-do item in this process: print and carry a copy of my 1Password Recovery Kit. It's probably also wise to create a second copy and leave it with someone you trust and can contact, just in case you are stripped of literally everything.

Wrap Up

With memorable passwords for iCloud and 1Password, and a copy of my 1Password Secret Key, I feel sure that I could get back to a working system from zero.

The to-do items for me that arose form this thought experiment:

  1. Change my iCloud password to something memorable.
  2. Register some additional Trusted Phone Numbers with Apple for my Apple ID.
  3. Create a portable copy of my 1Password Emergency Kit.
  4. Have methods of getting in touch with the owners of my other Trusted Phone Numbers if needed.

Certainly, what I have proposed here is the absolute worst case scenario I can think of that doesn't involve my being personally incapacitated or killed. Digital estate planning is a whole other consideration but the basics will be similar to what I have presented here.

What's new in Apple Classroom 2.0

With iOS 10.3, Apple have released Apple Classroom 2.0. Apple Classroom first shipped alongside iOS 9.3 and provided tools to help teachers in an iPad-based classroom.

Apple Classroom provides a range of features including observing student screens, launching apps and URLs and locking student devices.

In the initial release of Apple Classroom, the way that the system worked was that your school Mobile Device Management server had to create and send an "education payload" to teacher and student devices. This payload included information about which users are teachers and students, and which teachers teach which classes and so on. This also prevented students from downloading and using Classroom to control other students' devices.

This made it very easy for teachers in such schools to just pick up and use Classroom. Unfortunately, it made the job rather difficult for school administrators and MDM vendors. So difficult, in fact, that most MDM vendors simply have not shipped support for Apple Classroom. As a result, very few schools are using Apple Classroom to its full extent.

Apple Classroom 2.0 goes a long way to fixing most of these issues.

Infrastructure Changes

Previously, the infrastructure requirements for Apple Classroom were reasonably high. You needed an MDM server that supported the Apple Education payload and student devices had to be supervised. Essentially, that describes a managed school deployment.

Apple Classroom 2.0 can now work without any of these requirements being met, albeit subject to a range of privacy limitations.

At its most basic, now, anyone can download the Apple Classroom app from the App Store and set up an ad-hoc class. However, the degree of control is limited because of privacy concerns. In Apple's terminology, these ad-hoc classes are called "unmanaged classes" and the MDM-provided classes are called "managed classes".

When a 'teacher' creates an unmanaged class, the class availability is broadcast via bluetooth. A new Classroom section appears in Settings where students can see available classes and join them. There is then a code-based confirmation step, as in many such enrolment systems, and then the 'students' are now in class.

The nice thing about this is that only the teacher device needs to have Apple Classroom installed. The client-side software is built into iOS 10.3 so, as long as all devices are up to date, there is no need to coordinate everyone getting the app installed before you can get to work.

Unmanaged classes, once created, are persistent and by default students will automatically re-join classes when the teacher opens the class in their Classroom app. This can be changed in Settings so that students have to be prompted to join the class before a teacher can control the device. Students can also un-enroll from classes at any time.

As unmanaged classes can be created on any device, the 'student' devices have a lot more control over their visibility and privacy than do students in managed classes provided by a school. In the first place, students can simply not enrol in the class. Secondly, the student has control over two privacy settings: "Lock Apps and Device" and "AirPlay and View Screen". These are two settings, each of which control two features.

Each of these settings has three possible values: Ask, Always and Never. The default for both is Ask. When a teacher tries to lock a device or view a screen, the student sees a permission dialog where they can "Allow" once or "Always Allow".

In a situation where a school has devices supervised in MDM but their MDM does not support creating Managed Classes, there is a restriction that removes students' control over these two settings so that they cannot refuse locking or screen viewing. This is only applicable to supervised devices, so that generally implies institutional control.

It's also worth mentioning that managed classes and unmanaged classes are mutually exclusive. You can't mix and match. If a teacher device has an Apple Education payload installed by MDM, it will not be able to create any unmanaged classes. Similarly, if a student device has an Education payload, it will not be able to join unmanaged classes. Under iOS 10.3, a student in a managed class can look in the Classroom settings, see which classes they are in and see which teachers have access to that class. The privacy controls for locking and screen viewing are hidden in this scenario.

Teachers in BYOD schools where the iOS deployment is not managed in any meaningful way might wonder whether the more general availability of Apple Classroom presents any kind of security or privacy problem for teachers if students were to come into school with Classroom installed on their devices.

Honestly, I don’t think so. In order to exercise control over another iOS device, the ‘teacher’ device has to create a class. The owner of the ‘student’ device then has to:

  • Unlock the device
  • Go to Settings > Classroom
  • Tap on the class name
  • Enter a code that’s only displayed on the ‘teacher’ device
  • Be accepted into the class by the ‘teacher’ device

That’s a pretty difficult process to go through accidentally.

The other question is about students creating their own unmanaged classes to control other students’ devices. Again, this would require the setup steps mentioned above and students can always delete any unmanaged class that is causing them difficulty. If your school has Apple Classroom support in MDM, turning it on prevents any problems.

Teacher Features

The major focus of Apple Classroom 2.0 is the loosening of these infrastructure requirements. The update also brings a few new features for teachers.

Firstly, the class list has been redesigned. This now allows you to reorder the classes and is a much more compact representation than the simple screen-wide table view of Classroom that was in Classroom 1.x.

The single new feature in the class view is the addition of a button that will immediately mute all the devices in the class. I'm sure this will be a welcome addition for many teachers! This is simply an action that sets the volume once but doesn't lock it.

The bigger feature in Classroom 2.0 is the enhancement to AirDrop. Classroom 1.x had a Share Sheet extension that allowed you to share URLs from Safari to your class. Classroom 2.0 takes this idea and supercharges it.

Classroom 2.0 has the idea of the "current class". That is, the class that you currently have open in Apple Classroom. This is why the "Close" button in Classroom has changed to "End Class".

While you have a class open, the system-wide Share Sheet gets a new trick. The current class, as well as any sub-groups that you have defined, appear as AirDrop targets at the top of the sheet.

What this means is that teachers can now share a URL, photo, video or any file, to the entire class in one tap. This far exceeds the capabilities of the old Classroom Share Sheet extension that only allowed sending URLs to students. Now, anything that can be AirDropped can be sent to the entire class in one go.

Between Classroom 2.0, recent enhancements to Swift Playgrounds and the new "education edition" 9.7" iPad, someone at Apple is clearly listening to the needs of education.

Using Amazon Workspaces for Legacy Software

One of the courses we teach in school is Administration and IT. This is a Business Studies course that covers many of the regular office (and Office) skills that students might need in the future.

The course doesn't explicitly require that you use Windows Office but in practice it does. The exams are set by people who use Windows and the exams are marked by people who expect to see the output of Microsoft Office....so.

So I had the problem of having to somehow provide a Windows environment to our iOS devices. There's no way I'm buying and maintaining a legacy Windows lab for this course, so what to do?

There's also no way I'm getting into enterprise software land with services like Citrix. It's one of my basic rules that if the price isn't on the website, it's unlikely to be a price I'm happy to pay.

Enter Amazon Workspaces.

Amazon Workspaces is basically a virtualised Windows environment that you can connect to from iOS, Mac, etc. Best of all, you just click a button and you get a service - no salesmen involved.

We also have an Office 365 service set up for pupils taking this class. We don't have a general Microsoft license, so we're paying about £1.15 per pupil per month for this.

One of the things with all of Amazon Web Services is that you need to understand both the technical aspect and the pricing model - and you really, really, have to understand your own usage model.

For us, we use the VMs during class and rarely outside of class. For the Higher class, that's 5 hours per week. For the lower-level classes, it's 2 hours per week. It's quite a minimal amount of usage, so you can understand my reluctance to commit a lot of capital to this.

Workspaces has two pricing models: monthly and hourly. For the basic "Value" bundle, which is all we need, the monthly price is $27/month. The hourly pricing model for WorkSpaces is a basic $8/user/month to have the VM set up and then it's $0.23 per hour that the workspace is active.

So you can see that for us, where our usage is quite sparse across a week, the hourly pricing is a huge win.

WorkSpaces also provides a bundle where you can get Office 2013 built into the bundle and set up. What I didn't understand going into this, though, is that there is additional pricing for having Office installed in the bundle. That extra is $15/bundle/month. Considering we were already paying for Office 365, this was a huge waste of money.

My first deployment model was to put out the pre built Amazon "Value Plus" bundle. That was very easy to do but adding on an additional $15/user/month was too expensive. I didn't realise this until the first bill came in but once I did, it was time to make a change!

As part of the rebuild, I decided to create a custom image to create the student images from. I simply followed the tutorial steps and built a bundle that included the Google Drive sync app, Google Chrome, Office 2016 and Acrobat DC. I had previously led pupils through building their own setups but, as the number of pupils has increased, this is increasingly impractical.

Once I created these images for each student, all the student had to do was sign into Google Drive and sign into their Office 365 account.

Additionally, I tagged each instance with a tag named "class", so that I could identify the images associated with each class group. Essentially, the script enumerates all the workspaces with a specific tag and then sends them a start or stop command, depending on the parameters sent to the script.


None of the pre-built Amazon images are ideal for what we want. In particular, we wanted to have Google Drive, Chrome, Acrobat Reader and the latest version of Office installed.

So I followed a fairly simple tutorial to create a custom bundle for our students that included those packages. All the student had to do to make a bundle work for them was to sign into Google Drive and Office and they're ready to go.

This custom image should also make it easier to delete and recreate the workspaces. To save money, I will endeavor to find some months in the school year where we don't need to have those Workspaces in operation and delete and recreate them. I haven't done that yet, but it's more of an option now that setup is much faster.


This is where things start to get fun. When a user tries to connect to a stopped instance, the instance will automatically start but this can take up to 5 minutes. This ain't exactly what you want when trying to get a class started, so I decided to try and figure out a different way to do it.

First, I wrote a python script that would start or stop each class group of workspaces on demand. This script lived on a unix machine we have in school. That was helpful - as long as I remembered to run it before class.

Of course I rarely remembered to run it before class. Remembering to do things is a computer's job, so let's get the computer to do it.

AWS provides a service called Lambda. Lambda allows you to run a Python script in the cloud without having to worry about anything to do with the server or the underlying operating system. It's basically "scripts in the cloud" and very helpful for small self-contained scripts like this script that starts and stops groups of Workspaces.

So I wrote this script and set it up as an AWS Lambda script. The question then was how to schedule it to run. Turns out, AWS has another tool for that: CloudWatch.

Cloudwatch is the monitoring and logging component of AWS. In general, the primary use case for CloudWatch is to monitor your AWS workloads and take action. For example, if your response times are getting long, CloudWatch would notice and run a Lambda script to spin up more servers.

CloudWatch also contains an option to execute Lambda functions on a schedule. There are options for running them on set frequencies (once every X minutes) or on a Cron schedule. This latter option is perfect for my application.

I didn't want to write different scripts for each class group or for starting and stopping workspaces. Instead, these needed to be arguments passed to the script. CloudWatch scheduled rules allow you to send parameters to a Lambda function in the form of a JSON dictionary.

So I set up each rule to spin up the Workspaces 20 minutes before the class starts and stop them 10 minutes after it ends. This was a bit of a hassle, as it requires two rules to be scheduled for each period - one to start the servers and another to stop. Still, at least it was only a matter of changing the Cron expression and the parameters sent to the Lambda function.

The only major wrinkle here was that CloudWatch scheduled rules always run on UTC and there's no way to express a local time zone. This is a pain as I now have to both adjust all of my CloudWatch triggers when the UK reverts from BST to GMT and, worse, remember to do it.

So, in summary, the chain of events goes like this: CloudWatch executes on a Cron schedule to run a Lambda function which causes AWS Workspaces to start or stop.