High school's a lot different here, but it was a lot better than primary (high school starts at 11 here) and I did most of my non-work programming while at high school.
So long as you remember to knuckle down when the work matters and for exams, you can enjoy your time outside of school. The more you pay attention in class the easier the whole experience becomes.
As for the people. You'll probably only see a handful of them ever again, so don't worry too much about impressing the idiots, and make friends with the people you really like.
I think you'll find it's a bit like a scary film, the lead up to watching it can be a bit tense, the first time watching/day there, can be a bit scary, but after you've done it a couple of times (few days/week) it's not scary, and just boring
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