LOL I've never heard of that before.
Well I'm guessing what happened at your school was that a couple of kids were caught doing something not appropriate for their age, so they gave the entire school "the talk".
In terms of legality, if some kids of similar ages (within 1 year of age usually) get caught engaging a form of sexual activity that isn't appropriate for their age, the school will likely first determine if there is any parental abuse going on, if not, they won't throw the kids in jail, lol. It's technically illegal and yes, there could be law suits, but the usual course of action for kids who are "just experimenting" is to sit them both down, and explain the risks of underage sex (i.e STD's, pregnancy, etc). Kids do stupid stuff sometimes, unless one of them was much older than the other (i.e a 16 year old and a 13 year old), explaining that that kind of behavior is inappropriate is enough in most cases. I have never heard of kids being thrown in "juvy" for anything less than repeated theft or assault.
So I'm pretty sure if there's a lot to debate about in the subject, it's probably a better idea to avoid that subject as a debate.