Well, I'm not condoning or proposing any particular method of sex education in schools as I don't know what the best way to handle it is, but as a general rule, leaving kids to figure stuff out for themselves on topics they're embarrassed to talk about, or worse, think it's wrong of them to want to ask, often really isn't the best way of doing things. In the UK we're talking about ~2% of the population, so I don't think there needs to be a massive deal made about the specifics of it, but teaching the 98% that the 2% isn't evil, wrong, perverse or abnormal can't be a bad thing for anybody, or at least any reasonable person. Most of us want to be in a sexual relationship at some point, why not give everyone an open and honest starting point in terms of knowledge early on in life.
Besides all that, kids these days are learning about sex from hardcore porn, if you're worrying about your kids not having sex the way god intended, that's what you should worry about, not what they teach in schools.