The psychological harm and confusion.
Exposing children to age inappropriate sexual material can actually cause kids to experience earlier puberty than would otherwise happen. (Told to us by a PhD psychologist friend of ours).
Until the hormones kick in, it’s better for the boys/girls to think that the girls/boys have cooties.
Sex is for adults, not kids.
Yes, that is a documented phenomenon. It's very interesting piece of information about the brain's affecting the rest of the body.