Alright, I think I'll just say my peace about this issue and then crawl back into some little corner of the forums where I'll... I dunno. Rot, I guess? :V Right, anyway! (Still gonna check back on this thread, though... I'm a stalker like that ;D)
Let me start by saying that, yes, I think the middle school age is too early to become sexually active. At all. I can understand kissing, but beyond that it just becomes too much for someone of that age to bear the responsibilities of. I'm probably being a bit hypocritical, as someone who's... "made mistakes," we could say, at that age. But when I was that young, trust me, I didn't know what I was getting into. I didn't know what being in that sort of relationship really meant at the time, both emotionally and socially. So, I definitely think that the focus should be on discouraging those sorts of relationships by showing the very real effects of them; the physical, emotional, and social. Not "wait until marriage," but more along the lines of "you're not at a good age to start those things yet." Unfortunately, that's not what I was taught as a middle-schooler, and that's what led me into doing some things at that age that I sorely regret now.
Now, with that said, I don't think education should ever be abstinence-only, even in middle school. Because, let's face it; you can give a kid all the information in the world about sexuality, but some of 'em just don't listen (I've heard of more than one pregnant teen, even within the early teen years; it's very disheartening to hear about). I feel like middle school kids should, therefore, be given information about contraception in addition to the fact that, no, contraception is not 100% safe (even if it works most of the time, if used correctly), and that there is emotional baggage to be had in a sexual relationship of any kind that, at that age, most if not all kids just aren't ready for. If nothing else, at least, this might help them prepare before they engage in sexual activities later on; better than a girl finding out she's pregnant one day and saying "oops look like I got preggers OH WAIT I COULD'VE USED A CONDOM WAT?!" (...Okay, perhaps not that extreme a situation, but hopefully my point still stands.) And as for the kids who'd just go and have sex anyway... well, if someone was about to jump from a plane and nothing you said could stop them, wouldn't it be better to just give them a parachute instead of watch them plunge to their certain deaths?
tl;dr Discourage middle-school kids from doing anything sexual using facts about the consequences, but teach them how to be safe for later in life and also because some kids won't listen anyway.
So, that was my long-winded reply, bahahaha... |D;