Welcome to the modern world. This type of behavior happens all the time now.
My wife works at a middle school. They have special teachers just for the BD kids. One of the BD teachers recently broke her ankle, but this wasn't school related. Anyway, one of the kids got pissed at her and kicked her twice in her broken ankle. The worst part is that she doesn't have a cast. She didn't want one and was trying to get by without it. What was done about this? Nothing, the same nothing that happens to most kids who assault teachers. This kid was already on "Level 1" and had the cruel punishment of missing out on certain "privledges". So, in other words, he didn't really lose anymore privledges after his attack. Ouch, huh? That will really teach him a lesson, right?
And this is a nice suburban school, this isn't some inner city school.
The teachers have their hands tied. They can't even really defend themselves. They have to just "restrian" the kids until they calm down. Basically, they can only hold the kids down when they get out of control.