Not in high school, but in middle school we had a little story. A friend of mine had a knife he used to carry around and generally take it out every now and then to show off. Then one day, we were doing the good citizens' work of keeping kids out of the locker rooms during the break. One kid wanted to stay in, didn't like being thrown out, connected the dots, and the next day my friend was threatened with expulsion for, as the kid said, "violent threats with a knife", or however you word it.
He somehow managed to avoid it though.
And the students one year above us were a bunch of dongs who liked to gang up on people after school. So we ganged up too and there was a bit of a scuffle. Didn't reach the news-worthy level, but a few injuries happened and they never did that again. Fun times.
EDIT: Oh yeah, we also decided to take justice into our hands when valuables left in locker rooms started mysteriously disappearing. We made the life of a cleaning lady living hell, and she promptly left. Cruel, I know, but guess what? Turned out she really was the thief.