How well do we know our children?

MILES AND Margo O'Brien thought they knew their son. He was 21 and a former altar boy. He liked soccer, hurling and a drink. He'd had the gumption to leave rural Ireland and look for work in London. They thought they knew him until 12 days ago when they opened the door to the two local police officers who had come to tell them he was the IRA bus bomber.

Tom Greenhow thought he knew his daughter as well. She used to like swimming and ballet. She was 23 and had a first-class degree in physics and astrophysics. Ten days ago she killed herself in northern California, leaving behind a suicide note addressed to her gun - "the only one I'm reluctant to leave behind" - and a hundred pages of rambling notes revealing her obsession with neo-Nazis.

How, you wonder, could these parents not have known? Didn't the O'Briens think it was odd they had no address for their son? Didn't the Greenhows notice their daughter's propensity for wearing paramilitary uniforms and her fascination with vampires and life after death?

They must have been wilfully blind or just plain stupid. Except, of course, that young unemployed men do leave rural Ireland to seek work in London, and often move around from place to place. Why give your parents an address if you're never long in one flat and you're calling them regularly anyway? Edward O'Brien rang home every month.

And young women do wear strange clothes, dye their hair orange and paint their fingernails different dark colours, as Jane Greenhow did. Her father, a 50-year-old executive with the Ministry of Defence, prided himself on being close to his only child. He and his wife, Blanche, visited her regularly when she went to Leicester University: "Jane wore black a lot, but nothing paramilitary, and nothing she said ever alarmed us."

There ought to have been clues. In retrospect there were. Jane Greenhow shot herself following the suicides of her friends Ruth Fleming and Stephen Bateman at a shooting range in Mesa, Arizona. Fleming and Bateman left behind right-wing photographs, pages from firearms magazines, chillingly cryptic notes and a medical cardon which Fleming had filled in her name as "Obergruppenfuhrer Stattspolitzei" and her address as "hell agony eternal". They, like their friend, were dressed in paramilitary uniforms.

But maybe the clues weren't so obvious at the time. Bateman had been Jane Greenhow's boyfriend in her final year at university. "He seemed shy and well-spoken," her father recalls. "We had no reason to disapprove of him. Jane seemed quite happy with him. He wore combat gear but we thought that was a kind of hobby, and there was nothing bullying or aggressive about him."

The two girls, best friends at university, both took first-class degrees in physics and astrophysics. Then they they got jobs in computing, an industry with a future. They shared a house in Andover, Hampshire, with Stephen Bateman. All three were apparently embarked on an interesting and adventurous trip across the United States. They must have seemed to their parents to be doing everything right.

Edward O'Brien had sold the odd republican newspaper, but a young man in a southern Irish country town with sympathy for the republican cause is a million miles away from being a terrorist. In the words of his parish priest, he was "a clean-cut young man ... devoted to his family". He had no criminal record. His deeply religious mother would have remembered her altar boy; she would have had no reason to assume he had become something else entirely. His last reported words were on the phone to her, a few hours before he died: "See you, Ma, I love you."

It is easy for adolescent and young adult children to appear to be doing what their parents hope and expect. Like the parents of Leah Betts, who died after taking an Ecstasy tablet at her 18th birthday party, the parents of Greenhow, Fleming, Bateman and O'Brien missed the signs. Leah Betts's parents thought they'd talked to her enough about drugs. They thought she didn't have anything to do with Ecstasy. They were wrong. It's easy to be wrong.

ADOLESCENCE is a time of secrecy. Sex, drugs, violence, shoplifting, friends: most spirited teenagers do things of which their parents would disapprove, and don't find it necessary to reveal the fact at home. Occasionally, however, they adopt a whole set of secret beliefs. It isn't easy to discern at what point the locked diary, the whispering with friends on the telephone, the mysteriousness about where they are going ceases to be the normal business of adolescence and becomes sinister.

Young people break the rules. It's one of the rules. Parents, unless they are foolish, must expect not to know everything about sex and drugs. But the thought that your child might have a violently distorted outlook on the world is more disturbing. So how can you tell? Can you ever be sure?

Psychologists often give a pat answer to this question. They may put it in a more prolix way, but basically what they say is "it's good to talk". Dr Mark McDermott, a lecturer in psychology at the University of East London, says: "You have to ask in what circumstances adolescents become secretive. There are still a great many Victorian and Edwardian parenting practices: ideas that parents must be respected and are there to administer punishment. If young people think the atmosphere is punitive, or that their parents are indifferent to them, they will retreat. So if you think your children aren't communicating with you, you have to ask: 'Am I unapproachable? Do I get irritated when they want my time?' Parents have to be sponges. They mustn't be judgemental."

This sponge theory of parenting is not particularly helpful, except to those who don't have children or have come out of the other end relatively unscathed. They can conveniently heap blame on those whose children collect neo-Nazi memorabilia or turn to bomb-making; they were too judgemental, or alternatively, they were indifferent. To those who are actually going through it, and know parenting is also a matter of setting boundaries, if only so children can test them, this ladling out of blame will only induce panic. And it doesn't lead anywhere, except to the banal conclusion that there should be more communication. We knew that already. That's the point: you can't be sure, even when you think you're communicating, that you really know what's going on.

It is unrealistic to suppose there is some ideal state of family life in which teenagers would tell their delightfully understanding parents everything. Often the secrets are kept for a good reason. Masud Hoghughi, a consultant clinical psychologist in County Durham, carried out research at the Royal Grammar School in Newcastle, in which he discovered almost all the pupils commit some ritual act of shoplifting when they leave school. They don't tell their parents for the perfectly sensible reason that it's better for them not to know. The teenagers know it's wrong and they're not going to make a habit of it: why present their parents with the moral dilemma of what to do about it?

The attraction of youth culture - the music, the drugs, the different beliefs - is partly that parents don't understand, don't have the vocabulary. Half the excitement of it is that it belongs to young people themselves. To let parents in would be to ruin it.

As for being non-judgemental, it's an unrealistic ambition. You can, for example, accept that teen magazines such as Sugar and Just 17 impart useful information, but still dislike their parent-troubling language of snogging, mates and lads. You may accept that, on balance, they're benign while still wincing at the idea of your 12-year-old daughter, who was so recently only interested in ballet, reading a magazine with the cover line: "What makes a girl like you sell sex". And it may be quite important to make this judgement, and articulate it, otherwise how will children ever be able to make fine distinctions of their own?

The other problem is that after a certain age it becomes impossible, practically speaking, to have the full and free communication recommended by experts. Once children move out of the family home, as the three young neo-Nazis and Edward O'Brien had, you can't know for sure who their friends are or what they talk about.

Reassuring as it would be to believe that parenting is a science, an experiment that fails because the ingredients were wrongly mixed, the truth is that it is more of an art. There are no pat answers.

YOUNG people are natural idealists, looking for ideals. And never more so than now, when, for example, a teenager growing up in the London Borough of Newham is surrounded by 53 languages and all the cultural diversity that implies. There is no homogeneity, and there are no automatic ideals.

Parenting has always been carried out by more than a child's mother and father, but in settled societies all the adults surrounding children will have an instinctive understanding of where the process is going. In modern, fractured urban society, adults can't agree among themselves, and have in any case their own worries about employment and relationships. The peer group competes for influence, and the peer group is subject to all sorts of cross-currents of ideas, many of them ruthlessly commercial.

Peter Wilson, director of Young Minds, the national association for child and family mental health, believes technology is developing so rapidly "it is difficult for young people to get a clear idea of what the future holds. The idea of a long-term career progression is not applicable. They have to worry about Aids, global warming, drugs, violence. They have a very different mental set from their parents. Contrary to popular belief, I think they are very moral. They're struggling to deal with dizzying amounts of change: it's not surprising they feel they need beliefs, a cause."

A cause may take the form of environmentalism on the one hand or neo- Nazi fantasies on the other. Mental health professionals sometimes express this rather more elementally. According to Dr Arthur Hyatt Williams, retired chairman of the adolescent department at the Tavistock Institute: "Both the life instinct and the death instinct are very strong in the young. Armies have always exploited this to fight wars, and the IRA does it now. So does extreme nationalism. The wild mood swings of adolescence explain why dangerous driving and dangerous sports, drugs, guns and fighting can seem thrilling to young people."

The Seven Million project, a research project run by the think-tank Demos into the values of the 7 million men and 7 million women aged between 18 and 34, suggested that on the whole young people are more inspired by the life instinct. They reject authoritarianism, rigid moral codes and traditional politics in favour of equality between men and women, hedonism and strong opinions about specific issues: the age of consent, poverty, New Age travellers, roads, or crime prevention. But the project also found more diversity than in previous generations, and a minority that had moved hard in the other direction, towards racism, nationalism and violence. It is expected that these findings will be supported by another large research project, from Barnardo's, which will be published on Friday.

It is this second group of young people, who are looking for certainty in nihilism, who are the subject of the film Kids, which has caused controversy in the United States and opens here in April. The film depicts a couple of days in the life of middle-class, urban American youth: sex, drugs, HIV, violence. The overwhelming impression is of an autonomous youth culture with no contact with parents, or even reality. Young men who have participated in a scene of stoned, pointless violence discuss it almost as if they'd experienced it through the electronic media. They are the children of the "me" generation, of liberal parental attitudes and the parenting deficit. When one girl rings her mother to tell her she's HIV positive, she can only reach her seven-year-old brother.

Adolescence is a time of insecurity, now more than ever, and insecure people feel safest with a closed system of belief. This may take the form of a conviction that Take That are the best band in the history of the world, or it may lead to dressing up in black uniforms, playing with guns and flirting with the far right. You have to communicate: you have to devote more time and effort to your children than to anything else and listen to them even when you really want to be thinking about something else. But you also have to hope. Because it's difficult to find out what's going on without seeming interfering, and once you seem interfering, it's even more difficult to find out what's going on.

Questions you may not be able to answer

1) What is the most important thing, person or activity in your child's life?

2) Where were they and with whom last night?

3) Have they ever stolen anything?

4) Would they find it easy to approach you if they

were in trouble with the police or at school?

5) Do you know what your children

believe in?

6) Do they want you to know?

7) Do you mind them having secrets?