My dear friend! Many people many times felt just the same as you do right now, I'm not an exception. This is a widespread problem of bad self confidence. And this problem is solvable! If your friends think you're a snob, then go ahead, make them think differently. Walk into the classroom and smile to your classmates, say hello to everyone. It's scary only for the first time. And don't worry about their reaction, they're just surprised. If you're still too shy to do that at once, then do it another way: go to an after school activity. That can be sports, music, drama, anything you choose will fit. There you'll get to know different people, it will be easier make the first impression, just because they don't know you and they won't judge you by the things you did before, like the classmates can.
So, here I finish my letter. I hope, those advices can help you.
Always yours *имя*