Oh and I have had to restrain a 14 year old with ADHD in a rage. He was already taller and heavier than me, but I managed it and got him calmed down. If I can do it, a trained police officer shouldn't have any problem.
That's absolute rubbish. Firstly just because one child with adhd can be calmed down by you doesn't mean all can. Or that all react like this.
Note that Deathclaws said she restrained the boy before she calmed him down. As she rightly points out, if she could restrain a boy who was taller and heavier than her who was in a rage, then it should not be beyond the wit and indeed strength of a trained, fit police officer to restrain a 12 year old girl safely.
I'm bemused at people who suggest the officer isn't much bigger than the girl. He blatantly is, and he has to be around twice her weight. Plus, as a trained officer, he's clearly strong.
One of the things that concerns me about that clip is that he immediately picks her up and makes her walk. She's just been thrown down onto the pavement and was concussed. That seems incredibly dangerous.