ah, i see. i'm sorry that school is so rough for you

how long do you have left? what are your goals after school? before you can plan what actions you want to take, you should figure out a tentative plan for the future so you know what you're working towards. i would recommend enlisting the aid of a trusted adult for this

i'm unfamiliar with the french system of education; is it possible to drop out and take a certification that is equivalent of graduating? (generally, in the US, this would be frowned upon, but would be worth it if the situation is as bad as you're describing, i think)

all that said, you likely can coast and do minimal work and at least graduate. if you're being harassed by someone, you should report them / tell them to stop / basically go out of your way to avoid them, or cause problems that are clearly their fault (although that can be difficult). it may also be worth talking to said trusted adult about this issue

teachers being vapid is pretty much out of your control, but just because they're vapid doesn't mean the material is. if you take an interest in learning things for the sake of learning, and digging beyond what they give you in school, you can at least attain valuable knowledge about the various subjects of your classes

this is part of what i learned in school myself; even though you're forced to be in school, you're the only one responsible for if you learn something or not. so learn the ways you are able to and get what you can out of the environment. maybe french high school is super difficult, but you seem like you have a good head on your shoulders. you should be able to learn stuff well enough to pass

still practice the breathing, exercising, etc that i mentioned, though. this:

And right now, I’m so fed up this existence of student, trapped in the petulent academic system that I can even focus anymore. I can’t think, I can’t write, I can’t remember.

sounds like you losing your executive functioning to stress. your anger at the situation is valid, but you need your brain to be online to cope with it and get out. take a step back, breathe in, hold. release as slowly as you can. repeat

try to notice when you're spiraling with emotion, try to remember to breathe when you are. it's hard at first but over time you'll notice it quicker and be able to respond in the moment

you'll make it out one day. just focus on getting there