Mark Steel: You can teach birth control but you'll end in hell if you do it

How can there be so many lunatics opposed to sex education? And apart from anything else, what makes them think a lesson about sex is going to make kids go out and immediately have sex? It's education about it, not an instruction to get it done before dinner break. Maybe they should demand an end to history lessons as well on the grounds that "I don't want my fourteen-year-old learning about Napoleon as he's too young to invade Italy."

It took institutions as irrational as the Catholic Church to make their objections, so a law was devised making sex education compulsory. But now, after "Extensive lobbying" from the priesthood, an amendment's been added that religious schools will still be able to teach their own unique Biblical version. For example, according to Ed Balls, Schools Secretary, the schools "can still teach contraception is wrong, but they can't refuse to teach it."

So that's an improvement I suppose. The Catholic teacher can demonstrate putting a condom on a banana, saying "First we expel the air, then place it over the end, then we remember if you do this for real you'll face an eternity in unimaginably agonising molten lava searing through your pores as you scream in soulless anguish while demons submerge you in relentless unbearable horror, then right the way along, nice and snug and we're done. Now you try."

If the only rule is that they have to teach about sex, but it doesn't matter if it's in any way true, the religious schools might as well teach anything they like. They could tell the class "Copy down these facts - 1) Doing it from behind makes your tongue fall out. 2) Masturbation causes earthquakes. 3) Every time you get an erection you poke an angel's eye out."

There's no other subject that schools would be allowed to teach with their own version of the truth. If a teacher told his class "Some people believe the capital of Italy is Rome, but I've always said it's Nairobi in the North Pole", they wouldn't get an Ofsted report saying "He might be teaching geography that's cobblers but he's teaching it, and that's the main thing."

Religious schools will probably try this trick with other lessons now, to see what they can get away with, refusing to teach chemistry as they don't believe in sulphur, or announcing they won't teach the six times table as the Pope's had a vision that it's wrong.

So we're left with differing methods of approaching sex education. One might be to acknowledge that we get desires, that can be lethal at times, so it's probably for the best if we find ways of managing them safely and respectfully. Or there's the more traditional method, which is more along the lines of "You know those natural feelings you get – well they're unnatural so stop having them."

They might as well teach that God wants everyone to be cold, and if we feel a desire to shut the door in winter we must fight the temptation, and we must go to the park in January in our swimming trunks to and, if we shiver or reach for a coat, that's Satan at work and we should discuss it with the priest.

This might do less damage than teaching sex education that involves pictures of sexually transmitted diseases, and stories of the decrepit life that awaits anyone who submits to sexual temptation. Imagine the outrage if people in favour of sex education resorted to those tactics, by saying "This is what happens if you stay a virgin all your life", and showing a picture of Ann Widdecombe.

But somehow it's when sexuality is most denied and suppressed, that you find society most riddled with torment and horror, of abused children shipped out of the country to avoid embarrassment and hushed up illegal abortions and all the things that God doesn't seem to mind as long as no one uses a condom.

But then the government probably isn't bothered about the social implications of their policy, as long as the schools get good exam results. They won't mind if the Catholic school turns out a heap of screwed-up teenagers as long as they get A grades for correctly calculating the angles in the holy trinity.

In any case it's probably all irrelevant, as most schools manage to make lessons excruciatingly dull whatever the subject. So it could be a sex education lesson about responsibility in relationships, using the problems of Ashley Cole, and by the end everyone would be staring out of the window as the teacher bawled "Come on, we ought to know this, what's wrong with Ashley's texts? Well, before he writes 'then make you scream like a hyena' there should be punctuation. No wonder he's in trouble, now write it out as he should have done."