I've said this before, but who's to say the kids aren't learning about reproduction from, say, human body books? Those are a thing in real life too, so what's stopping kids from reading them and learning where babies come from? Or do the parents/school just tear out the pages on the reproductive system, and that's why sex ed is a thing? (I've heard the pages taste just like that Bambi tape.) Not to mention, we also have Google, in case kids are curious to know anyway.
As for the part about girls maturing, I can kind of see where Enter's coming from - when I was in middle school, the girls in my year level were generally taller than the boys. However, as we see from elephants and giraffes, taller doesn't necessarily mean more massive, and I think that's where the fallacy comes in. (Not sure which fallacy, though - false dichotomy, perhaps?) How is Enter such an idiot when it comes to writing scripts?