I agree with everything you and meridian have said, except for this part. Sex might be a big thing; and for most people, it will be. But it's very, very important that sex-ed lessons don't isolate, exclude or stigmatise the not-insignificant minority who feel that sex really is just another kind of physical activity, just as it's important to not exclude people who, for example, don't want heterosexual sex, or who don't want sex at all.
just another kind of physical activity
That's sort of tautological: every human activity is physical in nature, even thinking. Perhaps you mean "just a sport" or "just a workout"?
Let's assume it is just a sport. Well, sports can and do get you killed, or worse, maimed and/or in pain for the rest of your life, sometimes by accident (and carelessness and ignorance
increase the risk, but
some amount of risk is
inherent, and is always considerably greater than in most activities that aren't "sports"), and
sometimes by design.
Yeah, sex will cease to necessarily be a big thing that should only be had after serious consideration just as soon as the risk of STDs and unwanted pregnancies is eliminated. In addition, humans seem pretty strongly predisposed to form emotional attachments to people we have sex with, and I seriously doubt this is entirely a cultural phenomenon.
The main consideration when having sex is that you are both in the same place mentally. Given how sex can run an enormously wide gamut in terms of what it means to a person - a bigger range than almost any other act that I can think of - it's essential that it means a similar thing to both parties. If not there's the potential for enormous emotional fallout that a few minutes of pleasure will simply not have been worth. If the sex is throwaway to both parties - fine; If the sex is deep and meaningful to both parties - also fine. The problems come about when one party misrepresents the significance of the act either to the other person or to themselves.
A secondary consideration is that orgasms release Oxycotin causing you to bond a little deeper with the person you just had sex with. If that person would be a crappy long-term life-partner then having sex with them might be a pretty bad idea - even if for both of you the sex is initially just about having a little fun. (Another thing that our super-duper sex-ed class needs to teach is that being in love isn't a good enough reason for two people to marry or even to be together; Compatibility of personality, world-view and life-ambition are as important if not more-so.)
I can't possibly stress how right all of you are, and how important it is that kids be taught about these points. There's just one aspect of sex that you're forgetting:
"Naughtiness". "Doing the nasty". "Bumping uglies". "Getting freaky". These metaphors aren't just a result of cultural frameworks. Sex entails Smells. Fluids. Sounds. Breath. Strange sensations. Strange, nonsensical behaviors. The feeling that your body isn't yours, somehow, that
it's moving on its own. Sex a powerful Dionysian force against Apollonian rationality, of civilization, of control and deliberation and judgment. (
Unless you've got specific training...).
Education is about learning the
Apollonian skills and knowledge and judgment that will help us to properly grasp (understand, get, weight, evaluate, hold, control, constrict, own) our Dionysian instincts, compulsions, cravings and passions, in order to become, not a bundle of contradictory wants and feels and stirrings, but to
ride and steer and manage them, to become free individuals, able to make informed choices, and able to make the best use of the reality of their bodies, both mechanically and physiologically (emotionally), to achieve maximum happiness. That is the fullness of wisdom, that is true, final adulthood. It certainly and undeniably involves the loss of innocence, that is to say, blissful ignorance.
And I believe children should not be denied the tools to reach it as soon as they are able to, lest they remain children, on a certain level, for the rest of their lives.