Man, I felt so much the same way, bro. Highschool, for me, was kind of a joke. The important thing is, though, that you finish. Get your diploma and do your best.
The same thing happened in College, but it was a lot less pointless - and much harder.
Most of the stuff you learn in highschool and college is more "training your brain", than actual numbers and facts.
The thing I learned most in college was how to learn.