Are the children in your class overweight, over-sexed, physically unfit, and violent? If they suffer from some or all of these defects, allow yourself a little glow of satisfaction. Bringing up the next generation is a joint exercise that involves schools, parents and society in general.

Schools do not do a perfect job - and get enormous flak for their imperfections - but have more or less kept their eyes on the ball for the past 20 years. Yet society in general (and, I fear, many parents) is making the most dreadful hash of things.

Modern capitalism sees a child, almost as soon as it can walk, as another profit-making opportunity. Children are now the fastest-growing consumer market and they are bombarded with images of supposedly desirable things to eat and drink and images of supposedly desirable ways to behave.

Since the modern child spends at least as much time at a television or computer as at school, perhaps the Office for Standards in Education needs a twin: an “Ofchild” that would inspect what happens to children when they aren’t in the care of teachers?

Slowly, we are waking up to the damage society is doing to the next generation. We think that, just possibly, if they see a succession of violent acts excitingly presented in films and computer games, children may think violence is fun; and that, if the fashion industry designs sexually provocative clothes for children and the entertainment industry creates pop groups to titillate them, they may start having sex too early.

The latest discovery of common sense comes from the Food Standards Agency.

It warns that rampant child obesity - the result of eating too much junk food - will reduce life expectancy for the first time in a century. Type II diabetes, which can lead to heart disease and kidney failure, and was formerly confined to the middle-aged, is now being diagnosed in teenagers.

And the agency properly connects cause and effect: children eat foods and drink drinks crammed with sugar, fat and salt because they are advertised and sold to them with single-minded ferocity. Not only in supermarkets, on television and through sports sponsorships, but even in schools. Who thought it was a good idea to get Walkers to sponsor a “books for schools” scheme, based on collecting tokens from its crisps packets? Are we all mad?

The Food Standards Agency wants more regulation and, in some cases, prohibition. Fat chance (pun intended). Tessa Jowell, minister in charge of media regulation at Westminster, fears a ban on food adverts would mean “far less money to spend on programmes”. What she really means is that the Government dare not take on the food industry, just as it dare not take on the entertainment industry over violence and sex targeted at children.

Instead, she blathers on about more sport in schools, when it should be as plain to her as an iced lolly that an hour in the gym or on the playing field will make little difference.

She also talks about “educational initiatives” to help children “decode” advertising. In other words, teachers as usual will be asked to make amends for society’s failings. When they fail, they will be roundly denounced.

To write about this subject is to risk sounding like a killjoy and a food faddist. I am neither. I do not wish to deny children their sweets. I merely think that, like most things in life, such foods are best taken in moderation, as part of a balanced diet.

Likewise, in writing about sex and violence, I do not wish to be mistaken for one of those dreadful people who write in the Daily Telegraph, advocating virginity until 25 and demanding that theatres take the blood out of Macbeth. But I fear that, if society is to make a better job of raising children, I and many other liberals will have to run such risks.

Peter Wilby is editor of the New Statesman.