Really, I don't see what people are so shocked about. There's nothing wrong with kids that age who want sex. I would say that if anyone is at fault for their early sexual activity, it is not the kids but the parents, schools, the media and wider society. Nobody ever talks about sex in a matter-of-fact way to kids. And if they do they are somehow seem to be 'polluting' their minds, or something similar. Of course all this is assuming that there's something inherently wrong with people that age having sex in the first place.
Looking back at my own school years, I would say that if I had the opportunity at that age to have sex, I probably would have taken it. It would've been too bad if I had had that opportunity then though, because at that age I probably didn't know much about safe sex or contraception. I certainly wouldn't have known how to obtain contraception, in any case. Because contraception wouldn't have been easily available to me, chances are I would've made someone pregnant and in the process contracted an STD. (Of course this is all hypothetical).