Solution: Outlaw knives.
With that out of the way, we continue.
I teach at the largest school in the state of North Carolina. Just last year, we had a minor altercation involving a tennis ball escalate to a group beatdown. Two students were tossing a ball down a hallway, and it got away from them, hitting another student. This student got angry and somehow this lead to him being beat down by the two original kids and a friend of theirs. The victim was beaten so badly that there was blood all over the lockers and hallway, and he needed several reconstructive surgeries on his face.
This sort of thing is isn't frequent enough to be called pandemic, but it does happen, and it's always appalling. I don't know that I see an immediate solution because it's the result of numerous factors from gang involvement to racial tension. At the risk of oversimplification, I think you can distill it down to people not understanding what's proper when interacting with others. Each is so quick to take a defensive or aggressive stance that it's often difficult to resolve things peacefully. On the other side of that, where a mostly harmless, cathartic fight might relieve some pressure, untapped aggression takes control because students don't just argue and bystanders don't just stand by. The students want to seriously harm one another, and their friends and peers want to instigate these fights.