I'm thinking of leaving school
Why would you want to leave instead of finishing?
I don't like the teachers and my classmates in this school, in fact I hate them all.
You should try to stay in school. It is about your future, not about your classmates or teacher.
I'm doing a petition against the teachers.
As long as you decide to stay in the end though. I think that it is bad if you do not finish when you are already so close.