For one, if the teachers are making comments, you need to go to the principle. Their job is to help you with your self esteem not knock you down. As for the other kids, I know this is easier said then done, but ignoring them is the best thing to do unless it is getting physical like them trying to touch you in an inappropiate way. I got picked on all the time in school because i had a lazy eye. I would ignore it and they would stop after a few days. It seems like they would go thru a cycle of people that would get picked on for the week. I don't know why kids are like this. I have read from many psychological stances that it begins at home. If the parents pick on the kids or allow siblings to pick on each other, it spills over into the school.
All of the school shootings we hear about are from kids being bullied and picked on. While many schools are implememnting programs to deter bullying and making fun of each other, I think parents need to be more involved with their kids too. Too many parents just let their kids go.