The police should have told the school administration to piss-off...
You seem not to have thought of the parents of the girls in this matter. What if such handling of their daughters is offensive to the moral bearing and family dignity of the girls.
My counsel to the parents of the girls would be to remove their daughters from such an educational system where boys are allowed to “greet” females in such ways. But if, for some reason, parents have no alternative, how would they be protected from such boys?