Well Im not sure what advice I can say as this ha never happened to me, I was the guy in high school that stuck up for the guys like you because I was friends with the ones that picked on people like you... I guess I slowly turned the whole thing better..
As others have mentioned you have to stick up for yourself, try talking to these guys. You are obviously a very intelligent guy so use your intelligence. Heck if they have an XBOX tell them you will mod the thing for them and Give them a shit load of games for a small price..
Use what you have in your power to beat them down or to be somewhat of friends with them, so that they will stop. Its obvious that they are not happy with them selves so they have to belittle others to make them selves feel better. Next time you take a beating make sure your at school, and alot of the women in the school and men are watching.. If they see it do you think they will like the guys that are doing it? no they wouldnt.. On the next note if that happened, you would see many more people likely sticking up for you, and these jocks will become hated. Not to mention if you get your ass kicked again, tell the fucking guys you will see them in court and sue there parents, this will give you enough money to get the hell out of your city:
But most importantly you have to talk to people like your family and friends, and counsellers at school, talking to us online will give you some advice, but you ultimately will have to speak with someone face to face. TRy not to go home from school by yourself, go with a friend or something...
You will have to come up with some way to just stick up for yourself, but in an intelligent way that wont get you beaten again.. Sure you could go and shoot the guys, but what is that proving? that wont help you in anyway, it will only damage you in more ways then what you are all ready feeling. We dont need another Columbine on our hands, when yet something as easy as talking to people could solve it.
I hop that I have helped, Im not sure what more I can say, if you need to talk more PM me and I will reply. Best of luck. Keep your head up high, stay smiling..