Finally, most people know that sex is procreation and how to do it. I doubt, however, that most people actually know the biology behind it. You should not be teaching the pleasures of sex, but rather the biology behind sex to a child.
Most often, those who know about ####s and vags and what not don't actually know some of the basic biology behind them. Such as, but not limited to, you do not pee out of your vag, virgins can have broken hymens, and hymens aren't always broken during ### semen is not the same as sperm, and they probably won't be able to identify most parts of the reproductive organs.
So, unless you're teaching them about that, it's best to leave the educating to your health teachers, and not take the education into your own hands.