I certainly don’t think that many of these incidents would have ended in a court case.
I would estimate that in England in ordinary mixed schools in say 1970s, the slippering of pupils would probably be 80% boys on the receiving end, and of the twenty percent of girls who were slippered at school perhaps 80% would be slippered by a female, but that still leaves quite a lot of incidents like the one described by Phillip. I think this would have been the case for my school, where girls were threatened with a slippering by the headmaster as a harsher punishment than being slippered by the female deputy, this was usually for repeat offenses and extreme naughtiness.
Different schools had different rules and traditions, but I imagine that my school was quite typical.