What we need to do is educate them.
And by that I don't mean some beslubbering stupid video about "Johnny Condom", or some 40 year old explaining how the penis is around from placid to erect via physical or mental stimulation.
I mean teaching what sex is about; how to do it, how to get other people to do it, why people do it in the first place, the risks, the rewards, and so on.
Sex education for me, as far as I can remember it, consisted essentially of "boys have a penis, girls have a vagina. You must not have sex at all until you're 30 and married!" Yeah, like that'll stop teenage pregancy. Come on, when I started sex-ed me and my friends laughed at the word "vagina". We didn't take it seriously, we weren't ready to, on any level. Sex needs to be something we are told about when we need to know, not when we just hit puberty and are still wondering why the hell we aren't allowed on the climbing frame anymore.