I don't think he had was in the right to just start shouting at them. I mean, I couldn't tell entirely what they were getting in trouble for, but it didn't look right.
Considering he had him on the ground, was pushing him around trying to take property off of him, that I don't believe should've been taken. Then he just started shouting and bellowing at them for no reason.
And I don't quite know if he's allowed to just shout at them and tell him to sit down, and even insult him.
Personally, whatever they were doing, it didn't look serious at all, and he just looked like a prat. I'm surprised they didn't report him to his police station for verbal abuse and un-needed physical contact, considering they weren't doing anything of harm, as far as I could see. Not to insinuate that something requires to be harmful to be wrong, serious or illegal.
He's also a bit of richard for coming up with insults/comebacks he seemed were smart. I don't know where it sprouted in his mind to ask "Do you act like this for your teacher?" because obviously you wouldn't. Because your teacher wouldn't wrestle you to the ground for a flimsy skateboard, nor would he shout abuse at you.
I don't know all the laws that are in that place, and I don't know the rights that PoliceOfficers have where he is, and I don't even know what the kids were doing in the first place to get him so riled up, but I do know that he went over the top, far beyond what he should have done.
Considering they're only 14 year olds.