That young girls use abortion as a contraceptive - a theory popular only among those who have never endured the procedure - is debatable. That the Government uses abortion as a political prophylactic is undeniable. A grim and fractional victory is the best that you can call 28 more girls under 14 last year choosing a termination rather than abandoning their childhood and prospects.

The golden government target of halving teenage conceptions by 2010 looks an awful long way off: just a 13 per cent reduction, then, in seven years. But abortion, the ministers' little helper, is at least knocking down the percentage of live births. It is easier to roll out morning-after pills and drop-in abortion clinics than to address the bigger, more controversial question: why can't we talk to our young people about sex?

At Experimentia, the children's science museum in Copenhagen, I watched a film on puberty. A graphic cartoon depicting erections, wet dreams and burgeoning desire ended, well, rather climactically. It was earthy but not pornographic, droll but not smutty. And yet my outer grown-up had to tell my inner child to stop sniggering. A very British reaction, I guess. It is hard to imagine such public blitheness in a London museum. Young eyes might see it, would be the horror, when, of course, that is the point.

Sex and children is still an almighty national taboo. This year a coalition of youth groups urged the Government to begin compulsory sex education from primary-school level. To read the outraged headlines, you'd assume that five-year-olds would be given subscriptions to Razzle, when any parent knows that curiosity about bums and bits and life's eternal mysteries begins early, and that a child will not be prematurely “sexualised” if you explain why ladies lack willies.

And yet even with 20,000 girls under 18 having abortions every year, teenagers are required only to label a diagram of the Fallopian tubes, not learn how they might avoid getting pregnant. Why do we allow individual schools to decide whether Personal, Social and Health Education (PSHE) is taught at all or to omit anything they find unpalatable - homosexuality, abortion - or parents to hoick children out of lessons which could, more than anything else they learn, affect the course of their lives?

A friend who teaches PSHE to 14-year-old girls received, as is normal, no specialist training beyond being handed a dusty folder. Thankfully, after three children of her own, she is unembarrassable, a prerequisite when answering “Miss, can you get Aids from giving head?” (Often PSHE is dumped upon the youngest, most bashful teacher.) After a few lessons of handing out worksheets and, that new educational cliché, asking children to design a poster, perhaps on the dangers of sexually transmitted disease, she ordered the girls to down pens.

No more writing, only talking. It became clear that the girls' knowledge of sex consisted of sexy images acquired from reality television, but little biology.

“Their idea of a strong, sexual woman seemed to be Jodie Marsh,” she sighs. Few believed that sex was meant to give them pleasure. Most were unclear that girls could even have orgasms. Sex was still - after aeons of supposed progress - what you let a boy do to you to keep him.

And it struck my friend that, since these girls did not understand why they desire sex, they could not articulate why they might say no. So she devised a lesson about the sneaky, underhand time-honoured lines boys pull to lure a girl into bed: “If you won't do it I'll go out with your mate”, “Don't worry, I'll only put it in the once” etc.

Such explicit discussions are thought by the moral alarmists - those also most agitated by the teenage abortion figures - to sanction under-age sex. But she was giving them the wherewithal to choose, to assume control, the social smoothness to fend off the unwanted fumble. And she taught them a sexual language that wasn't rude or funny, embarrassed or appalled. As international studies show, the more sex education they get, the later a child remains a virgin. The billions thrown into US abstinence programmes have done nothing to reduce a teen pregnancy rate even grimmer than our own.

As Mel, a teacher of vulnerable young people just out of care or prison, says: “These kids find it easier to have sex than to talk about it.”

But who doesn't. As a nation our Carry On-esque sexual mores ricochet between licentiousness and prurience: we sit through five series of Big Brother waiting for someone to fornicate live on TV just so we can condemn it as a moral nadir.

Opponents of compulsory sex education say that it is most appropriately conducted at home by parents. And you would think that we liberal baby-boomers would have no trouble doing “the talk”. But we had scant sex education ourselves and certainly I - even after recourse to frank Scandi-style reading matter - can only hope that I'm forging mature sexual beings not future cases for therapy. It is easy to suppose that today's teens with their bare midriffs and copies of Nuts have no need of our groovy-dad lectures.

Certainly a generation of young men are receiving their sex education from the brutal mechanics of internet porn. As one young guy told Mel: “No one wears a condom in a porn movie.” Unprotected sex must, therefore, be the apogee of pleasure, so girls, frightened of denying them, take risks and boys take advantage.

Since parents assume that sex is covered at school - or sucked up by cultural osmosis - ignorance is endemic. ChildLine receives 50 calls a day from young people seeking advice about sex; a third of girls are not told about periods by their parents. Too often the default solution to all shortcomings in our children - from binge-drinking to table manners - is to bung a new subject on the national curriculum, so compulsory sex education by trained, creative, unblushing teachers could arrest a cycle of bad sexual practice. And it would mean that the next generation of parents will not be as tongue-tied as we are.

The Government must stop hopping from foot to foot like a PSHE rookie and face up to the shrieking minority of religious busybodies and alarmists. Make them copy it out 100 times: “Sex is part of life - get over it.” The alternative isn't a class of cross-legged virgins, but clinics brimming with wan-faced girls.

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