All cower before me! (SPOILER)Sorry if I come off as too aggressive

Not all parents handle their kids that well, and understand that a parent has a lot more freedom in how to handle their child. While a parent could send the kid to their room and let them freak out and throw fits, a teacher could not. If the teachers in this situation were to, say, put the kid in an empty room until she calmed down, and the kid hurt herself in the process, the teachers would be at fault and would be in trouble. Teachers do not get this same freedom when handling another person's kid.

I know kids acting out happens, but this is way over the top and very overblown. Something is very wrong with her situation somewhere down the line.

The police were needed, though, because that child could easily have hurt someone else or herself, and then, again, the school would be in trouble. Calling the police in situations like that is the best thing to do, because they have more resources at their disposal, and more rights when it comes to handling other people, even children.