The number of teenage pregnancies has fallen – in England it is at its lowest for 20 years, although Britain still tops the league for western Europe. However, according to government figures released last week, the rise in teenage abortions has risen noticeably. Half of pregnancies in girls under 18 end in abortion; for girls under the age of 16 there has been an increase of 10% in the number of terminations. For girls under 14 there has been an increase of 21%.

This bleak news has given rise to the usual calls for the government to introduce mandatory sex education in schools. At present the only legal requirement is that children should be taught human reproduction, which is part of the science curriculum. Some of the more vociferous organisations are calling for mandatory sex education and “relationship” classes from the age of five.

What I’ve always found really extraordinary about these constant cries for more sex education is the underlying supposition that children and teenagers are unbelievably stupid and that the 6ft 13-year-olds you see lummoxing about don’t know how babies are made.

Let’s assume the poor things really are all simple-minded, although in my experience that is far from the case. Surely even they could manage to remember four little facts? 1) Ejaculation can lead to conception; 2) if you use a condom you (generally) don’t get pregnant; 3) condoms are free from family planning clinics and this is how you put one on; and 4) this is all hypothetical since you don’t have to have sex if you don’t want to.

That’s it. The end. You could teach it in 10 minutes – five if you talked quickly. In fact it’s hard to see how you’d eke out these four crucial bits of information to fashion sex education lessons over 11 years, from five to 16, or why anyone would particularly want to: sex education classes, where they occur, are piercing agony for the teacher and a giant snigger-fest for pupils.

Besides, there’s always PSHE (personal, social and health education), which includes a module on sex and relationship education. (And which leads to this kind of conversation, which I relay verbatim: “Hello darling, what did you do at school today?” “We had PSHE.” “That’s nice. What did you learn?” “That masturbation is a healthy thing.” Cue hysterical giggling from children and their mates.)

Now obviously I’m happy my children aren’t taught that masturbation will result in a lone, long black hair sprouting from their palm (as a friend of mine believed until university) and that they know about human reproduction (it turns out that my eldest son, who sat a biology GCSE last week, is something of an expert on the menstrual cycle).

I’m perfectly happy for them to be instructed further – I wish all boys would have PSHE lessons about internet porn and respect for women, for instance – but I don’t actually think it’s the school’s job to provide them with this kind of information.

I’m perfectly in favour of compulsory sex education, on the basis that information is power and on the basis that any given school will have within it a number of pupils whose parents deliberately keep them in the dark (although even compulsory sex ed isn’t a guarantee of enlightenment since parents – those whose religion prohibits their daughter from acquiring essential information about her own body, say – can choose to withdraw their children from classes, wrongly, in my view). However, I don’t think going on and on about how we need more of it is the right solution.

What we really need more of is parental responsibility, and extra sex ed only where that parental responsibility is observed (by schools or social services) to be wholly absent. Basically we need parents to talk to their children and for lines of communication to be open. When I was a teenager, my mother observed that I had a serious boyfriend and said, “If you’re old enough to have sex, you’re old enough not to get pregnant”, and sent me off to the family planning clinic (not being a complete ninny, I’d taken myself there a few weeks previously). That was it, job done – and I’ve never been pregnant accidentally.

Not, by the way, that I think all teenage pregnancies are disasters: as you read this I will have been at my goddaughter’s baby shower; her mother had her at 17 and it was lovely. My own mother also had me at 17; that seems to have worked out fine too. There is nothing wrong with having babies at the optimal biological age – but only if you want to have them.

What I can’t believe is vast numbers of young women getting pregnant by mistake. I just don’t get it: how hard is it to use a condom or even to totter down to the chemist to get the morning-after pill?

Everyone’s always going on about the Dutch and their marvellous approaches to this subject – sex ed from kindergarten basically and few unwanted teen pregnancies. What nobody ever says is that the Dutch aren’t hung up about sex and consider it a normal part of life, to be discussed en famille.

You could argue that this is because they’ve all known about anal sex from the age of six, but I don’t think that’s the real reason (or perhaps it puts them off so massively that they’re in no rush). Despite their sex club/pot head reputation, the vast majority of the Dutch are rather old-fashionedly upright in their morals and have a big thing about order and rectitude. That, combined with a robust attitude to how normal sex is, is why they’re not overburdened with pregnant 12-year-olds, I would suggest.

In Britain we moan about how sexualised young children have become – which they have – and jump to the stupid conclusion that physical or sartorial precocity equals sexual precocity. Why should it? It’s the adult equivalent of thinking the girl with the biggest bosoms in the class is a slut simply because of the way she looks. We think it anyway and cringe from initiating any kind of conversation about what may really be going on.

We comfort ourselves with platitudes – kids grow up so fast these days, they know so much . . . The truth of the matter is that a child who has sex aged 12 does not do so because she loves shagging but because she is insecure and can be pressurised, or because she is insecure and wants to be loved/admired/ gossiped about/infamous. This is what needs to be addressed and it is what would make far more difference than years of sex ed. And that is a job for parents.

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