I want to tell kids at my old High School that most teachers there are useless and that they need to depend on themselves
Why would you plan on doing that?
I just don't want them to do the same mistakes that I did.
I think you have good intentions with what you're gonna tell the kids from your old high school, but I just don't feel like criticizing your teachers it's the best way to do it. Your teachers are doing a noble and decent jobs, and it is not fair for you to criticize them especially if they haven't done anything wrong. Why don't you just tell the kids too depend on themselves more, without criticizing your old teachers?
They can't go down the same road I did.
You can help guide he without bad-mouthing teachers, who already have it hard.