MY best advice is to do activities that make you happy.
When i get involved in makes me feel like part of a time and it brings up my self-esteem.
I hope you find a solution

I think I know that you might be going through. And it's not easy.
Maybe, this is what helped me, every time you wake up in the morning, decide; is this going to be a good or bad day?
If you decide for a good day, don't let anyone get in the way of that, not even yourself. It might, or might not, be difficult.
It matters not what others think of you, and if you actually agree with them, then you need to ask yourself; "What's wrong with me?" and answer that seriously, and fix it. If you need to become outspoken, then start answering questions in your classroom(Your a good student right?) Then talk to people you don't normally do. If you think that your appearance isn't the greatest then I'd suggest thinking of what is wrong, if it's acne, wash your face(with soap) if it's your weight, then try running or walking someplace you enjoy, maybe there's a place close by that you can walk to.

But I think that you can't let the past actions of others get in the way of your own happiness. I bet you that they have the same insecurities as yourself, they just can't handle it as well as you can.

Yes I do Coach.
I found something that works, is raving across the world, is simple and extremely powerful.
Its called EFT (Emotional Freeing Techinique and it works on EVERYTHING. I mean EVERYTHING.
It will change your life.
www.emofree.com
Good Luck