The sight of Prince Harry, previously dubbed the Playboy Prince, cuddling an African baby with Aids could not have come at a better moment in a week in which a survey of teenagers told us that the number of depressed teenagers has doubled since … As someone who was a very depressed teenager indeed, and who has intermittently battled with what Churchill called “the black dog”, I felt the immediate pang of sympathy most fellow-sufferers feel. Isn’t it bad enough to have acne and A-levels without the angst as well?

Prince Harry is rich and privileged beyond the wildest dreams of most – but also bereaved and the product, like too many children, of a broken home. You might choose to think that his following in his mother’s footsteps as a high-profile charity worker is just a public relations attempt at polishing up a somewhat tarnished adolescence, but I happen to think it genuine. Earlier last week, the series That’ll Teach ‘Em in which a group of cynical, resentful, academically unsuccessful fifteen-year old were taught at a recreated 1960s secondary modern school. Stripped of their mobile phones and 21st century pseudo-adulthood, forced to call teacher’s sir and dress in unattractive uniforms, they not only had to sit much more demanding GCSE’s in Maths and English but learn practical skills. The girls learnt to type, bake and sew, while the boys learnt to milk a goat, bricklay and make a tea-tray.

The transformation in these teenagers was absolutely amazing. Not only did they get slimmer, fitter and much more attractive as human beings, they also cheered up and blossomed into radiant self-confidence. Boys who had been truanting and priding themselves on being cheeky and “hard” turned out to be simply brilliant at wood-work. Their astonishment and pride at gaining Grade 1 in GCSE was mirrored by the girl who, depressed as an academic failure, plugged away at typing and got a Grade 2. In tears of joy, she said that whatever anybody said, she knew now she was good at something – just like the two girls who turned out to be wonderful cooks. You felt quite certain that you were witnessing a life-changing experience which only the stupidest girl chose to turn her back on.

I’m all for academic rigour and an academic elite, but it’s been obvious for years that successive Governments’ obsession with academic results is a disaster for those who are not stupid but simply not wired up to do GCSE Maths and English, let alone go to one of the ridiculous universities that are supposed to make all young people employable – assuming they can even afford a degree. I suspect that many of those who have added to the numbers of depressed teenagers would find themselves infinitely happier leaving school at 14 and having a good old-fashioned apprenticeship – if these still existed – by which they could start earning a living and some self-respect. The real enemy of happiness isn’t just the pressure of sitting exams that many are completely unsuited to taking, it’s the idea that there is no alternative route into adulthood. Forced in on themselves, it’s no wonder that so many teenagers, despite the material privileges provided by parents, become sunk in apathy and self-pity.

They can’t be wholly blamed for this – after all, who is there telling them that there is a world elsewhere in which they will find purpose and happiness? Not schools, driven by league-tables, or parents, cowed by the prospect of perennially unemployable offspring. You can’t make camp fires and dance round them, as the kids in That’ll Teach ‘Em did, because that’s what little children, whose world they despise, like doing. You can’t do sport unless you’re either at a private school or attending one of the decreasing state schools not to have sold off its playing fields. Clubbing is expensive, and so crowded you’d have better exercise in a sauna. The old kind of clubs, like the Scouts and Guides are terminally uncool. No wonder the only alternative looks like Prozac, or the binges on drink, drugs and under-age sex for which our youth are internationally infamous.

Only 5% of the mental health budget is targeted at under-16s, which (to anyone who remembers how absolutely rotten being 14 can feel) seems amazing. Yet the solution to this kind of problem shouldn’t always lie with Government budgets and targets, but in ourselves as parents and children. When I was planning, on a daily basis, how to kill myself as a teenager, I was rescued by a quiet, wise man called David Butcher who taught wood-work. Being encouraged to do something practical instead of the academic work at which I shone made an incalculable difference to my moods. As soon as you can see something that was just a lump of wood become solid and useful as a bowl or a box, your own wispy sense of identity and sanity suddenly gets a great jolt of life-giving realism. All kinds of unhappy teenagers, including the actor Dan Day-Lewis, benefited from those lessons – significantly, he was one of the only teachers at my horrible progressive school to be called “Mr.” Butcher, rather than by his Christian name – as they did from his William Morris Socialism that persuaded many of us to get off our privileged bottoms and do charitable work.

The worst thing about depression is that it makes you completely apathetic, like the victims of the Spectres in Philip Pullman’s His Dark Materials, or the Dementors in Harry Potter. The very thing that offers your only chance of getting better – doing something – is the thing that above all seems absolutely impossible. When you’re having a bad time, you become enraged at being told to snap out of it, and thinking about the less fortunate is as much help as eating your vegetables while thinking of the starving in India. It’s paradoxical that teenagers, who are pumped full of hormones telling them to dance, mate and have fun are often the ones to suffer most from this horrible feeling. Yet the moment you compare yourself with a real, live baby raped and infected with HIV and lying in your arms, it does become impossible to feel truly, madly, deeply sorry for yourself again. Prince Harry is an extreme version of the way forward for kids who, left to drift at home with a gigantic sense of failure, sink into drunken loutishness unless redirected outward. The world is bigger and sadder than you are, and the moment that you realise it is the moment you start to become a grown-up.

Perhaps, though, the rest of the world is becoming like North London. An enchantingly witty novel by Kate Saunders, Bachelor Boys, is published by Arrow next month. Its premise, that young men are all beautiful but useless, lounging around as unemployed actors, park-keepers and bouncers while the young women pursue hugely successful careers, has already struck a chord with Anthony Minghella who has bought it for film. Saunders’s novel picks up the kind of conversation you hear all the time among chattering class mothers, which goes along the lines of “So Horatia is head of ICI is she? Of course. And Tarquin has a job as a life-guard at the Lido? How marvellous, well done him.” Of course, not every young man is as lucky as the two feckless Bachelor Boys, whose dying mother persuades a determined young woman with a relentless work ethic to turbo-charge them into pulling their fingers out. But then few of us have the kind of people Prince Harry had pushing him round Lesotho either – only the example he has set.