So Ed Balls has decreed that sex education will be compulsory. (At the moment, parents can opt out if they don’t fancy the idea of their little darlings being given the facts of life by spotty Mr Boil in a grotty classroom.) From 2011 the nanny state will be given full control of the birds and the bees (opening instalments from age five; no parental opt-out at all for 15-year-olds) and if you bunk off, you will be fined.

Sex ed has, of course, always been a bit of a joke. I have vivid memories of a flustered biology teacher showing 30 tittering girls how to put a condom on a boiling tube (the tube was rather puny, and the rubber sagged off it like an old balloon; poor Mrs W stuttered that it wasn’t quite like that in real life).

Of course, the point of all these lessons is to try to lower our place in the European teenage pregnancy league (at 41.9 per 1,000, it is one of the few areas in which we Brits come top). Despite 12 years of new Labour action — a so-called teenage pregnancy unit doles out condoms and morning-after pills — we still have more youngsters up the duff than anyone else. A 2004 study found that in areas with the most hardcore sex education, teen pregnancies went up.

Yet the government persists. The argument expounded by Balls is that knowledge is power: telling kids how it all works and encouraging them to use contraception is meant to enable them to say no or to take precautions. The government is very fond of pointing to Holland, where sex education starts at five from next year and is more technical than most Brits could stomach (primary-school children writing essays on reproduction; open discussion of sex) and where the level of teen pregnancy is low.

Is Holland’s success story just down to extensive sex education? Or could it be that, although the Dutch teach their children about sex in graphic detail, their culture — with its rigorous Calvinist and Catholic moral framework, strong family cohesion, low proportion of single parents and, perhaps most significantly, minimal state benefits for teen mums — sends out an unmissable signal that teenage pregnancy is a bad idea.

By contrast, in Britain a pregnant 16-year-old can expect about £200 a week in benefits and possibly her own flat. For girls with limited prospects, often the offspring of teen mums themselves, a marriage to the state is not such a bad option. The taxpayer coughs up while the girl gets the unconditional love and status that being a mum affords.

Perhaps our proliferation of teen mothers is not due to a lack of knowledge but the result of a culture in deprived communities in which becoming a young mum is a lifestyle choice.

The fact is that girls who have educational prospects, who stay on at school, who go to college, are far less likely to get pregnant than those who don’t. We need to use education to break the gymslip-mum cycle by raising aspirations, rather than by getting teachers to give sex advice and hand out condoms.

The Dutch model is also out of sync with Anglo-Saxon attitudes to sex. While the Dutch and Scandinavians talk about it in an earnest and sensible way, back in Blighty a kind of “don’t mention the war” silence prevails. Don’t believe me? How many sexual relationships have you had in which you never discussed the fact that you were doing it? It’s not that we don’t like sex; we just feel cringey talking about it.

However much Balls may wish we were different, the reality of many sex education lessons is that they are still excruciating for all concerned. (A friend says teaching PHSE to a mixed class of 15-year-olds is about as bad as it gets.) Of course, by the time they leave school, children should have been taught reproductive biology, the facts about intercourse and pregnancy and that it is better to have sex in a loving relationship when you are old enough to handle the consequences.

One senior politician told me that many parents are too embarrassed to talk to their children about sex and want schools to do it for them. That may be so, but I don’t see why Balls’s sex education has to start in primary school. (Although parents have a right to opt out, at this stage there are no separate lessons and PHSE is woven into the curriculum).

As a parent I feel strongly about this. My girls are four and seven, but already I can see that how, what and when you tell them about sex cuts to the quick of your values. On holiday for half-term, we were lucky enough to see elephants in the wild; two got frisky in front of us. The girls wanted to know what was going on. We explained that they were mating and that was how baby elephants were made. It was a natural and spontaneous point to start the explanations.

By contrast, a few weeks ago I discovered my seven-year-old with a Jacqueline Wilson novel about a girl who got pregnant; she had found it at the library. I thought she’d already read it and was really upset. Our culture is so sexualised that it is hard to hang on to your children’s innocence. Luckily she’d started on a different book, so I confiscated it. The idea that school will be able to galumph in on such sensitive areas from the age of five — when children can be taught about “physical changes to their bodies” and “different kinds of relationships” — doesn’t seem right. Or that from seven they learn about “puberty”, “civil partnerships”, “separation” and “how physical changes relate to reproduction”.

As the elephants proved, some times are better than others to explain these things; as a parent I believe that I should choose when and how that happens. Though not religious myself, I can empathise with those with strong beliefs and understand why they might not want their children being taught about divorce or homosexuality so young and by a teacher who didn’t share their religion. At the school my children attend there are several Somali girls who are so devout that even in primary school they veil their hair. Gay marriage, anyone?

Politicians know this is a minefield; it is no accident that the Tories (who will probably be in power by the time Balls’s proposals become law) have as yet made no comment. David Cameron has said that sex should be taught in the context of relationships and that such lessons should not be compulsory. We shall see.

The truth is that schools are once again being asked to compensate for the shortcomings of a minority of parents, but in doing so, they are stomping all over the rights of the rest of us to pass on the facts of life to our children in the way and at the time that we see fit. Balls, let sex start in secondary school.

eleanormills@sunday-times.co.uk

Times recommends

• Graduates move home to cut costs
• Screen tests are the future of exams
• Briefing: University funding