I can relate to you a lot from reading this! Starting from around Kindergarten I always had trouble "fighting back verbally" with other kids who used me. I wasn't the brightest student and I didn't look as great as the other students, so I was a target for many others; blaming, teasing, you get it. Around 9th grade was the worst time, especially Speech and Health Class. Usually, in my school, the same kids you had in Speech you had in Health (.5 semester classes). There would always be a group of kids (mostly the bratty I-think-I'm-popular kids) would pick on me just because I wore glasses and I had low self-esteem. I didn't look pretty or was social with them, so they thought they could do away with it. My "friends" were no help. They weren't close or anything and they thought it was something fun, so they never butted in.
After that hellish year, I'm in 10th grade. It stopped ever since. I'm surrounded mostly by respectable people and good friends. I stayed away from the bad influences because I know I can't bring myself to bite back, sadly. I suggest you stick with better people and avoid this kind of attention, but if it persists then talk with someone who will give you professional advice. Sometimes family and friend relationships cannot help with what you're going through, I've learned that the hard way. I hope that I gave you some kind of an idea~ ^_^