But that's an important life experience! I mean, virtually every day at work I have to deal with bullies who steal my lunch money... /sarc
We expect kids to learn to "deal with" stuff in school which in adult life would result in the offender being arrested and charged.
It is not normal to stick hundreds of children together in a building with maybe (and I'm being generous) 1/10th that number of adults around to supervise them. I think that through most of human history that would have been considered a ludicrous idea.
My daughter went to my old high school. It's a private Christian school -- the kids who are there had to work hard to get there, and they all want to learn. They're given a lot of freedom, commensurate with their commitment to learning.
It works pretty well. But that's not a normal population . . it's self-selected.