Go for authority. First of all talk to your parents, see if they support you on this. When I was bullied mine said "We can do nothing about that." so figure out if you are on your own. Next step talk to a teacher or a the principle about this, prepare yourself with a speech, not a simple whine, explain that your rights are being violated and you are being threatened. If they ignore you, do the worst - get a legal help, or threaten them with such in a official letter/email. Where I live, that makes any institution scared shitless. When they receive a letter from a lawyer they know things have gone serious and they will be forced to act. We live in the 21st century, seriously today there are far worse things to do to a person then to beat him up. Ruin everyone's future because they dared do bad things to you. And DO NOT FIGHT BACK, if needed run like hell. You speak of reputation, but I'll give you a list of people who don't care about it: The school (institution), the police, the legal system in general.