At the schools I went to, girls pretty much got away with everything as the teachers just stood around and did nothing to stop them, and boys who hit back were always told never to hit girls. I don't recall one time when a girl was told never to hit a boy. I'm not the only one here who has seen that.
When I was in school I don’t think I ever watched anyone hit someone of the opposite gender - honestly. I’m nearly 50 now, so maybe it was just a different time; teachers didn’t have to tell boys not to hit girls.