While i was in school i saw my friend being bullied. I mean, guys was calling him fag and those other things. Once he told me that he will someday revenge he actually did it. While there was summer and You didn't have to go to school he was training at gym. Same goes with every other day, sure he got a little down in grades, but not that much. At the end of school (hard to explain for you guys Polish school system, but lets say he was then 16 years old) he literally punch in face one of guys that was bullying him with words. They shut up for the rest of school (that was week or something till summer and then next school "level") time that left.
What can i say? If you want to, you can improve yourself and stop those bullies. You can go to teachers or you can do it yourself, but remember - using force should be last thing you think of.