Cant be myself at school...

I know exactly how you feel; lots of ppl are like this. I think the problem I had was always worrying about what other ppl thought, but I eventually realized that ppl don't care that much. They probably don't sit around and talk about how shy you are. Don't be afraid to say your opinions, listen in with another group, or talk to your buddies. Ppl generally feel bad for shy ppl and let them join in the conversation or sit next to them, etc.