Focus: How well do you know your teenage children?

Young teenagers are fat, stressed, drunken slobs who gorge on drugs and underage sex, to judge by what we see and read - from the disturbing new movie 'thirteen' to the latest medical research. But can the little darlings really be that bad? We asked kids from all over the country to tell us things they would never tell mum and dad. Hester Lacey begins this eye-opening special report by sorting the experts from the anecdotes to discover the truth about modern teenagers. Parents had better sit down ...

Sherry is 14. She belongs to a gang of girls in north London, the sort of young teenagers you see hanging around in bus shelters, sharing private jokes. The sort that thoughtful, liberal adults tell themselves cannot be as menacing as they seem. "We don't really do anything bad," says Sherry. "All we do is torment Jews."

A camera crew followed her gang for the documentary Rude Girls. "We go out and pull their hats off and look for money underneath," says Sherry. The programme also features a young teenager who tries to give up stealing cars because it clashes with having a baby. Rude Girls was withdrawn from the BBC schedules for legal reasons last week - just as cinemas began showing thirteen, a disturbing American film that charts the rapid decline of Tracy, a happy, hard-working teenage girl into a self-harming drug addict and criminal.

Tracy is fictional. But even as the film was playing on parents' worse fears, doctors from the British Medical Association (BMA) presented at a press conference evidence that the real-life children of today will be obese, impotent and addicted tomorrow - if they are not already. Their health is at serious risk from binge drinking, poor diet and sexually transmitted diseases, the BMA announced. Meanwhile the latest British Social Attitudes report found that far from being fresh-faced idealists, young people are far more self-interested than previous generations. Tony Blair is considering lowering the voting age to 16 - but when a newspaper published a manifesto written by teenagers last week, one despairing reader was moved to suggest that "the voting age should be increased by at least 30 years".

So young people are not what they used to be - when were they ever? - but what is the truth?

Sex. Teenagers have it. We know that. But the main concern for health experts is that increasing numbers are having it unprotected. The BMA report says the number of girls having underage sex has doubled in the past 10 years and one in 10 of those aged 16-19 is infected with chlamydia, a symptomless, sexually transmitted infection that can cause female infertility.

Louise Orpin, who recently collaborated with the National Children's Bureau to produce an interactive CD-rom on sex and relationships aimed at teenagers, encountered frightening sexual ignorance while researching the project. "Thirty-four per cent of teenagers think that a boy doesn't need to use a condom if the girl is on the Pill; 60 per cent of teenagers would be too embarrassed to tell their partner about an STI. One boy said he didn't need sex education because he looked at porn." She believes a comprehensive national campaign is urgently needed. "I don't mean that we need to scare young people, but we need to become much more open and less prudish. Putting on a condom before having sex should be as natural a reflex as putting on a seatbelt when you get in a car."

Parents want schools to take the responsibility for sex education, says Orpin, while schools want parents to do it. The result is that many teenagers do not get sensible advice from anyone. "Lots of parents assume their teenagers know more about sex than they do."

Some teens are very conscious of the shortfalls in their own education.

"We had nothing apart from the good old period talk," recalls Jenna, 16. Suzanne, 17, says that her lessons boiled down to, "this is sex; don't get pregnant". Chloe, 15 (all three girls are from the Medway towns), recalls a demonstration with a condom and a test tube. "We had a male teacher, looking down, all red in the face. When we asked questions, he got more and more embarrassed."

Suki, 15, from London, reckons rampant teen sex is a myth. "Magazines make you think everyone is doing it but they are evil to make you think that. My friend slept with a boy when she was 14 and then he broke up with her."

Health. Twenty per cent of 13- to 16-year-olds are overweight and 40 per cent of boys and 30 per cent of girls take too little exercise, says the BMA. Chronic obesity is linked to a host of other disorders, including diabetes, heart disease and some forms of cancer. Doctors are already seeing obesity-related diabetes, usually an adult-onset condition, in children as young as 13. Arron Telford, 15, says: "Our school has just refurbished the canteen and 95 per cent of people go for the burgers, not the healthy food. Fitness and health should be drummed in at school."

Mental health problems are increasing. The survey suggests that one in five teenagers is affected; one in 10 A-level students has reportedly considered suicide. The link between physical and mental health should not be underestimated, says Dinah Morley, deputy director of Young Minds, the mental health charity for children.

"Overeating, drinking to excess, drug use, early pregnancy and smoking are all tied in with stress and self-esteem levels." There has been a steady increase in mental health difficulties among young people over the past 50 years, she says. "We don't quite know why, but risk factors include broken families, pressure at school, the increased use and abuse of drugs, domestic violence and commercial pressure. Children today are also seen much more as sexual beings, with all the pressures that brings."

Young Minds would like to see the introduction of "one-stop shop" services which would supply information on contraception, employment, money and health.

Maya Ryan, 15, from Dorset, says the food issue cuts both ways. "Half the girls in my class try not to eat anything at all and the rest eat everything they can lay their hands on. It's a real mess. We are all so stressed out with coursework and exams half the time it's a wonder we're not all crazy. Perhaps we are."

Habits. Drinking and smoking are the two habits the BMA is most worried about. Binge drinking in particular damages health. Eleven- to 15-year-olds who drink get through an average of 10.5 units of alcohol a week and 25 per cent of 16- to 19-year-olds smoke.

Sophie Harrington, a personal adviser at Connexions in Gosport, Hampshire, works with children categorised as harder to help. "I come across this kind of behaviour a lot, and the lack of self-esteem among some teenagers is really worrying." It's hard work being a teenager, and they need to relax and recharge their batteries, she says. "But some overcompensate, have too much social time, and end up even more stressed as school work piles up."

Teenagers too blame stress for bad habits. "People who smoke and drink are trying to find the nearest door out from all the stress of school," says Arron, who does neither. "People need to be educated about coping with pressure." Melanie Mower, 17, from London, says it's too easy to get hold of drink and cigarettes. "Everyone knows that if you have the money, that's all the shopkeeper is interested in. Getting drunk and sick ought to put people off, but it doesn't. People see it as funny."

Danu Reid, 18, says: "What newspapers don't pick up on is that everybody smokes at 15. But most people give it up. It's pretty sad, not cool any more, when you're 18."

Politics. The latest British Social Attitudes survey points to a hardening of attitudes among younger people over the Welfare State. Among the 18 to 34 age group, only 31 per cent believe that more money should be spent on welfare benefits, and only 34 per cent are willing to see money redistributed to the less well-off. Around 50 per cent supported both notions in 1987.

"There has been a real shift in attitudes to welfare benefits," says Alison Park of the National Centre for Social Research. "Young people have become a lot less supportive over the past 20 years. They used to be far more positive than older people, now the opposite is true."

Alison doubts that lowering the voting age would lead to very many more votes. "Young people are less likely to vote than older people, full stop. They are thinking about other things. They are not worrying about taxes and hospitals and pensions; that comes in your twenties and thirties, not your teens. Lowering the voting age and making a larger eligible group would make the turnout percentage decline even further."

It's not that teenagers aren't interested in politics, says Danu, "but those Westminster issues seem dull and irrelevant. What we are interested in are the issues that affect us directly like health and education, and saying no to the war became cool".

Arron is a member of the Medway Youth Parliament. "We have a representative on every board in Medway Council, and they do listen," he says. "Recently the planners who were redesigning the local town centre gave us their plans to look at. They said that as the next generation they wanted to know what we thought." He does not support extending the vote to 16-year-olds. "It's dropping it on people too soon. Most of our idea of what's going on comes from the press. The media has the power to sway public opinion."

Money. We are living in a material world, and these are material girls and boys. All of us seem to have high expectations now of how much is enough. A recent University of Cambridge study found that 57 per cent of people earning more than £35,000 believed they did not have enough money for essentials, while 40 per cent of those in the £50,000-plus bracket feel deprived. Meanwhile, the starting salary of a newly qualified teacher is around £17,000; for social workers it's around £15,000 to £18,000.

"We have set up a society in which we see material rewards as proof of success, competence and worth," says Suzie Hayman of Parentline Plus. "That is why parents feel a failure if they can't give children the latest gadget, and what makes children so demanding. But it's like trying to live on spun sugar; it doesn't fill you up. The real need is for a genuine relationship between parents and child. What young people want most is to be valued and accepted. If that is not happening within the family, they will fill the void elsewhere, whether it is with material goods, smoking and drinking, sex, or anything else."

Mobile phones are now an essential for any self-respecting teenager, says Danu. "There is a lot of obsession with buying," she says. Lee Tucker, 16, has two part-time jobs to earn cash: he updates his dad's website and works at a local golf course. He is saving for a car. "I know people with the latest laptop or digital camera or car; one boy at my school had a new Mini Cooper for his birthday. I would love an iPod but I can't afford it and wanting isn't the same as having. I've got everything I need at the moment."

Aspirations. The Government is currently aiming to get 50 per cent of young people to go on to higher education. If that's the path you choose, it means putting your nose to the grindstone. Coursework is due, and able pupils might be handing in as many as a dozen important assignments. The current endless round of tests doesn't make life any easier for teenagers, says Suzie Hayman: "From an incredibly young age children see themselves as having to succeed, or being failures. It's not surprising they feel under pressure."

So what are they working towards? "After all the work I'm putting in now, it had better involve shedloads of money," says Melanie, who hopes to work in law. "Yes, I want to make the world a better place, but you can't do that till you've taken care of your own needs. I'd like a few Prada outfits and a couple of pairs of Manolos along the way."

"I want to work hard, get my A-levels, go on to university and be a business consultant. I'd like a comfortable lifestyle," says Arron. Lee wants to study computing, start his own business, and "be happy". Danuhopes to marry and have children. "I want a job that's part of my life, not something I just do for the money. The most important thing in life is to do something. I hate the idea of apathy. The worst thing you can do is sit there not being involved because you're afraid. I want to participate."

Young Minds parents' information service 0800 018 2138. Parentline Plus, free confidential helpline, 0808 800 2222 or visit www.parentlineplus.org.uk