A fully grown adult confronting primary school children aggressively is never going to be the right move
. You talk to the school. If that doesn't work, you talk directly to the involved children's parents (we have had to do this). If that doesn't work you inform those parents that you'll involve the police - which usually puts a rocket up their arse - and if they're still not interested then that's exactly what you do, because at the end of the day, it's still harassment and assault whether it's children or not.