Colin Young

I would also add that aside from the current mental health, staying too long in this environment could result in developing bad software development habits. OP is early enough in career to develop good habits and seems to have the drive to do so, therefore should get out for that reason also.

Here's a few studies that indicate locally owned businesses (at least in US/Canada) recirculate more of their revenue in the local economy

What is the cyclomatic complexity of the method? Having that number at least gives you something objective to talk about, and gives you a way to measure if refactoring is making improvements. It's widely accepted that higher complexity code is harder to understand and maintain without introducing bugs.

Anxiety aside, if your manager witnessed your colleague yelling at you, hasn't done anything about it, and your colleague hasn't apologized, you are working in a toxic workplace. Get out. Now. HR might be of help, but, personally, I'd have another gig lined up before approaching them. Much like @AllTheKingsHorses said, I doubt you'll have much trouble finding one.

I might add a little more prominence to talking to a psychologist or other therapist (their G.P. should be able to refer them to one also). In these situations it can be helpful to have a third party who isn't emotionally invested for perspective. @bio should also allow for the possibility that they are not in fact doing their best at school, but whether or not that is what's best for them is another matter. A professional can help them and their parents work out what is.