I'm always shy and nervous at school and worried about what the other kids think. but at other places i'm fine. how can i stop being so shy at school?

CBT: The first thing to know is that this is relatively normal and you can work on being less nervous. Usually when you are nervous you have a thought in your head such as "what if im wrong, i'll make a fool of myself." step one is to train yourself to catch those thoughts. Step two is to think logically about it. Step three is to replace that thought with a more reasonable thought.

Overcoming anxiety: You may benefit from a therapist who specializes in anxiety, but @ age 16 you may just need to develop a stronger sense of confidence in who you are. Often in our teen years we worry what peers think of us. Even some of the "popular" kids feel that way but hide it in order to look more confident than they are. Read "the four agreements" by don miguel ruiz for a different way to think about this.

High school can be: Difficult. If you are able to be more outgoing in other places, i would suggest that you get involved in after school clubs, sports or performances. Even if you don't want to try out for a play, consider becoming part of the stage crew. It's a way to make friends and interact with people outside class. It will help you feel more comfortable in school as well. Good luck and let us know how it goes.