I don't know what to think about sex really. I know that I've been told what to think by the whole spectrum, and that doesn't confuse any bit at all.
I don't think we should teach kids what they should think about sex. Concerning what to think, I guess the best way to get that across is to show what many different people think, to ground their views in a social context. I mean, you can talk about pregnancy and the biology all day, but it doesn't mean anything because sex to most of us is a social activity. Then again, showing what many people think about sex can get across the idea that sex is a big deal, and that's not something I'd want to get across either - there are certain things that I want to convince people are important, and sex isn't one of them. Not that it is or isn't a big deal, I just don't want me - or any one source really - to have an unfair share of actively influencing how someone thinks, I guess because there's no right or wrong answer.
I don't even think we should teach consent. Yes it's what we should do in practice and it reduces harm, but when we do that we're telling someone how to think about sex and how it should be done (initiation in this sense, not the physical act itself). The individualist (he's small i know) in me is saying no, we should leave that for people to figure out on their own.
Should we prevent sex? Sex is one of those things that only affects the people close to you and those you do it with - there's not really an economic incentive to do it or an impact from it, and I guess that much tells me that it doesn't matter in the sense that there's no rational answer. I do think abstinence, as taught as "you're a bit young and have to figure this out yourself" is a good idea, because it's rational in being safe not sorry. Is that depriving them of pleasure? What they don't know won't hurt them ;) I think a good way of putting it is "you don't have to have sex." Within that message is contextualizing sex with life as a whole, as well as an emphasis on consent :P
It's funny that people think of pregnancy as a side effect of sex. The biological consequence of sex /is/ pregnancy. Contraception to sex is the cure for the "disease" of pregnancy, the insulin to the diabetes XD