I think part of the problem here, and I'm recalling this from memory, is that there were four officers, and two were in training, which might be part of why the officers responded with the force they did. Young officers seem to be somewhat overzealous.
And it's entirely possible that the mother had a legitimate reason for being unavailable.
But it's my point of view that regardless of the number of principals or counselors or specialist that ANY school employs, the fact remains that when you have a child who is physically uncontrollable, the school is utterly impotent and restricted in the ways it can deal with that child.
In this litigious society, we've forced schools to resort to state/police action when it comes to any issue remotely physical. And I don't think it's the most efficient way to deal with these kids. But school employees are legitimately frightened of personal liability.
If it weren't for mothers like this, so happy to sue, then children like this could be dealt with entirely outside police intervention in the first place.
It's so ironic.