Speaking from experience and getting through many retarded teenage situations, I'd advise you to just inform the police. Regardless of what you do, this bullshit will never end. You can either keep fighting with them and potentially get yourself into legal trouble, or just advise the police and get yourself out of it. If you're actually 18 (at least in Canada), it's not worth getting a criminal record.
Once I hit the age of 18, I stopped trying to pick fights and whatnot, because having a criminal record pretty much means going nowhere in life. That, and violence is an bad solution for most things.