Every now and then you hear an idea that makes you sit up straight and think, that's it! It's so bleeding obvious - why didn't I think of it? It happened to me yesterday morning at 7.32am. And this was the idea: that schoolchildren as young as ten be given compulsory parenting lessons.

It was the Conservative Parliamentary candidate Shaun Bailey, a youth worker on the rough inner-city council estates of West London, speaking on the Today programme. John Humphrys's voice was full of moral bristle: “Teach a ten-year-old girl how to bring up kids?” he asked. Love that assumption that it's just for the girls, John.

Absolutely, replied Mr Bailey - being a parent is a privilege and not just a right; we should point out that it's going to be hard work. “We need to instruct our children in the realities of families. Lots of people have children believing it's going to be like a Barbie doll.”

Now, I know that this area is fraught with accusation and counter-accusation: you are unfairly branding youngsters, or their mothers, or even the foetus. Or you are nannying, or over-reacting, or being a middle-class snob.

But when you think about it, it's so obvious: if we want to deal with the problem of third or fourth generation children in unemployable, chaotic families who, like their parents before them, never stood a chance, you have to make the mothers think before getting pregnant in the first place.

There are so many, many schemes aimed at wising them up after the event. The family nurses scheme, for instance, which pairs dedicated nurses with the most vulnerable teenage single mothers from early pregnancy until the child is two years old in an intensive programme of support and education. It's been a great success in the United States and yesterday the initial ten pilot areas in Britain were expanded to another 20. Which is good news: the help is far better targeted than the Tory promise to give every baby 23 hours' worth of home visiting from a health visitor in its first five years. Still, it would be better were it not necessary.

The Government announced another new scheme yesterday: getting kids aged ten and over to sign good behaviour contracts, and give them mentors to help to tackle their problems. But you can tell that none of this stuff is working just by glancing at the press release rolling out of the Department for Children, Schools and Families yesterday. There is now a Government's Children's Plan, a Ten Year Youth Strategy and a Youth Taskforce Action plan, promising 20 Intensive Intervention Projects, 52 Challenge and Support Projects (“fresh emphasis on the use of Individual Support Orders and early intervention”), a network of Family Intervention Projects, Parenting Early Intervention Pathfinders. “Today we are also publishing the Aiming High Implementation Plan...”

All those projects, all those plans... and it is almost always too late: you can identify the children who are more likely to get into trouble at a later age, by the time they are 6 or 7, yet nobody wants to brand a child a potential criminal then by targeting them for help. You can see kids from poorer families beginning to slip behind from pre-school age. Or, as the family nurses scheme recognises, you can identify the sort of families likely to need extra support as soon as the mother is pregnant.

But what the Government should be trying to do for future generations is to stop the cycle. And that means teaching children, from as young an age as they can begin to understand - yes, ten, perhaps - about the realities of parenting, the responsibility, the cost, the consequences of failure and the joys of success, from the price of nappies to the effect of drugs on the unborn, the sleepless nights to the penalties for children carrying knives. You introduce them to the idea of a good and a bad parent, and their effects.

For some kids, this might be the first time they have seen that there can be an alternative to chaotic parental management. They might have had rotten experiences with their own parents; they will often have already effectively been parents to younger siblings. But it is all the wrong experience. They might know a lot about parenting, but not about what good parenting can be. They might not realise that they have a choice - to be a positive influence on their child or a negative one. They might not realise how essential their own role is going to be.

If teaching them all this deters them from becoming parents too soon, fabulous. If it makes them better parents whenever the time comes, great. If it puts them off for life, fine. Ministers might even find that it launches many more teenagers on a path towards professional childcare, helping to fill the gulf between official expectations of pre-school childcare provision and the reality.

I know what people will say: it is patronising. Well it's not if you include everyone in the lessons, and I know many unhappy children in better-off families as well as in poor ones. It's only patronising if you consider it an exclusively “poor” problem. Then the critics will say that it is dangerous, in that it might encourage the children to think they could try being a parent - to which I would reply that they seem to be trying anyway, but in ignorance.

And then they will say that it isn't the job of schools to teach this stuff. Well, no, in an ideal world it's not, but it isn't an ideal world and too often the family structures and the example no longer exists at home to teach it. Better lessons in parenting than those silly citizenship courses.

I rang my friend's ten-year-old daughter, who is wise and the best unofficial childminder I know. What would she think, I asked, if someone were to suggest that she and her friends be given lessons in how to be good parents? “I think it's a really good idea”, she said without hesitation. And what would the boys in her class think? “I think they would think it was nothing to do with them.”

And there, John, I rest my case.

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