stopped talking to you-- the awful "silent treatment."
Just like with other fights, however, the first thing to do is think about what's going on. Are there just two people at the heart of the fight, and everyone else jumped on board? Is this about two or more friends ganging up on someone? Is this a fight that affects you directly, or are you just involved because somebody expected you to pick sides?
Although it's hard to resist the pressure sometimes, try not to dive into a group fight just because your friends are. If you can, make it clear to everyone that you refuse to take part...and maybe you can be the one to encourage others to start working things out.
If you find yourself at the center of a group fight, it's up to you to start the process that will end it. Figure out who else is at the center, spend some time alone with them, and get talking.
When a group fight just keeps dragging on, it's time to involve a counselor, teacher, or other adult you trust. This does not mean that everyone's "in trouble." Most adults would rather help you solve the problem than just hand out punishments. Your school counselor has had a lot of experience helping groups of kids through fights, and can set up a "mediation" (mediation means finding a solution or compromise) for everyone.
Hopefully, after all of this, your and your friend (or friends) are ready to Make Up and Move On!