I don'-t know that it was over reaction, not knowing if there was any history of either of these 2. There being 2 officers on the school ground suggests there are big problems at that school.
Do I wonder if he could not have tried to talk them down/break them up? Yes, under normal circumstances. But were these normal?
If those two kids have a history, then I can understand why the law was there. Should the kids have been allowed to go at it? If they resent each other enough, no, because that is when their brawl needs to be broken up by someone whether it be a cop or a school authority figure so that the brawl does not escalate to the next level.