First thing I’d be doing is ascertaining the full facts & background, instead of relying on the gutter media to tell me what happened. I wouldn’t automatically assume this is bullying, for example, because not all fisticuffs at school happen without provocation.
If I found out I was dealing with unmitigated thuggery or ladettes trying to be clever, as a magistrate(and that WOULD be a police matter & not school), the girls would be spending a considerable number of weekends(at least 10) on community service, with highly-visible orange vest if desired.