I just want to add a few points to the discussion and keeping myself in a neutral position because I understand both side as both business owner and occasional Construct teacher.
As stated in the past, I don't love at all the subscription model I prefer to pay more but once. 
Ashley and 
Tom already went many times on this so I understand their reasons and I am not going to argue with that. I consider therefore the current model a "Constant".
Now, let's check the "Variables".
I haven't read the tread about what's possible to do with 50 lines, I am well aware of the potential of Construct on expert hands after using for over 8 years. However a student that is not only learning a new software, but that is learning about programming, game design and maybe even art and music, will create a lot of not optimised code. That's understandable. It's impossible that even with a good teacher they can optimise the code by themselves without being carried on hand by hand.
So we have 50 events, the layer and other limitations aren't really limitations for beginners, what can we do to improve it? My usual solution is to offer to my students that can't afford a C3 license (or that wants to play around with it before buying), to use C2.
C2 is still available in its trial version, it has 100 events and 4 layers and can export in HTML5. The game can be loaded on a school website, itch.io, GameJolt and so on. There is a lot of potential to showcase the game and there is still a lot of space to experiment.
Yes, it doesn't have the latest feature of C3 and neither its performance, plus it runs only on Windows. But, hey you get an amazing product that you can use for free without time limit and that you can get a good idea about how Construct works. Students can spend even 6 months straight on it or work on it occasionally without penalty.
I had some student that started with C2 free edition and then after a couple of weeks they were already convinced about its potential and bought the C3 license for one year.
I think this is the best card that give a good balance and lets everyone win. Teacher can do it without costs, students can have an unlimited time to play with the software and Scirra can get their good share of money when the student decide to become a real developer.
The ones that will not like the tool will just move on without giving bad advertising to Construct because they paid for something that they don't like and the satisfied ones will be happy to have access to all the other extra features that makes development easier, like families for example.