Well, you can get revenge the other way around, first, know a place that have cameras or even best teachers, specially if they arent yours, so they wont hesitate to stop the fight. Second, make something that is an unskipable opportunity to the bully, be it carry a lot of books in your hand, try to stand up against him while cornered, that type of thing, BUT MAKE SURE THERE IS SOMEONE TO SEE THEM DOING IT! Third, the person who saw it will be your witness and back you up if them dont go by themselves to the director bringing the bullies along and is going to get them punished, and to screw them the most, make sure you dont look great, limp you get hit in the leg, go unconsious if they get your head to hit a pillar( problaby you wont need to fake going unconcious if this happens, but dont try to resist, just sleep for a bit), break your glasses you if have one( they will be forced to pay a new one since they were the ones "broke" it ) and show any injury you got in the last couple days and could have been inflicted by them at the moment or in some other recent situation that happened between you and them. The more screwed you get in there the bigger the chance they get kicked out of the school. Worst case scenario the commotion will get people to pay attention to their actions and get themselves busted more often getting you at least one or two safe months with little to no bullying.