When I was in school back in the 50s and 60s a teacher would have simply suggested that it was not a good idea to share medications. They probably would have asked if they actually took the same type and if they did, that would have been the end of it except they probably would have been sent to the school nurse to make sure they were OK.
If they were of different strengths, the teacher would probably sent a note home saying what happened and asking if it would be harmful and if there was any chance that it would be for them to not share one again.
Kids had pills all the time for one thing or another. Nobody monitored or cared, they trusted parents to instruct their kids if necessary. We have fallen a very great distance in less than one lifetime.