The lobby of the National Missing Persons Helpline is an uncomfortable place to sit. The visitor is surrounded by an impromptu gallery of posters, all bearing photographs of people who are missing, most of them teenagers. Their faces, usually smiling broadly for the camera, beam out beside a terse description of their height, hair and eye colour, and the date they went missing. “Fourteen-year-old Janet may be in the London area. There is great concern for her safety.” “When last seen, Fatma was carrying a black duffle bag with ‘Take That’ written on it.” “Paul’s mother is anxiously waiting for news.” And so the grim litany goes on.

Last month 14-year-old Peter Kerry became the nation’s best known teenage runaway (see page 4). But his exploits in Malaysia could scarcely have been less representative of the usual experience of pupils who go missing. Far from making it to the Far East, most don’t even travel as far as the capital.

“London can be a very unfriendly place,” says Inspector Derek Millar of Scotland Yard, who leads a team of officers employed solely to look out for youngsters at risk. But eight out of 10 cases are not that kind: “They go and hide in the stairwell of the block of flats, or sit in an abandoned car on their own. They have a bit of space and then come back.”

Unlike Peter Kerry, who was missing for over a week, most under-18s who go missing are found rapidly - within a day or two. But even this short timespan can cause huge anguish for parents, and serious concern for schools. According to the charity, NCH Action for Children, which undertook a national survey on missing youngsters, some 43,000 young people run away each year in England and Scotland. One-third run away repeatedly and children in residential care are far more likely to run than any other group. How much time do schools spend dealing with what are known in Scotland Yard as “mispers” missing persons? And can anything be done to prevent children running away?

Keith Dennis is head of Shenley Court, a Birmingham comprehensive with 1,600 pupils. “It’s rare,” he says, “but there are those youngsters who go missing after some crisis in the home or perhaps an incident in school that they don’t want to go back and face their parents with. There is a significant role for the school in that. Our policy is that we try to have somebody available and with the parent or the family while the hunt is on.”

The last serious “missing” the school experienced was two years ago, when a boy disappeared for 24 hours. He had run away after a serious incident at school, for which he had been disciplined. On that occasion, Keith Dennis stayed with the family overnight, until the boy was found. “The mother found it comforting to have somebody there,” he says. “I don’t know how to describe the experience except to say I wouldn’t want it to happen very often. It takes an awful lot of emotional energy. I’d got my own anxieties about it as well - you ask, ‘have we gone too hard with this boy?’ But I don’t think we had.”

In practical terms, Keith Dennis could do little apart from supply police with the names and addresses of the missing boy’s friends - usually the first port of call when looking for a young person. But moral support may be what those left behind need most. It is the main function of the Missing Persons Helpline. “Some parents go running around with a battered photograph,” says Sophie Woodford of the Helpline. “Others can’t bear to leave the house in case the young person comes back. Parents are often in such a panic that they can’t think. They want people to be positive and helpful.”

When a child is reported missing to the police, their response varies according to the circumstances of the case. “If it’s a three-year-old who’s just walked out of the door while Mum was on the telephone, we would want a very quick description and every available officer would be put to looking for that child,” says Inspector Millar. “If it’s a 14-year-old, and it’s half past six at night and they haven’t returned home from school, that doesn’t require such an instant response. None the less it could well still be serious. ”

In that kind of case, the police want to know if the child has run away before, whether there was a row, if there’s a boy or girlfriend involved, who’s the child’s best friend. They then take a detailed description. “We would want height, build, colouring, hair length, what they’re wearing if known, full description of any jewellery,” says Derek Millar. “Ultimately, we are looking at a very detailed description.” If the missing child is found dead, identification might depend on dental records or birthmarks. “But that isn’t something we would want to be expressing to a worried parent at this stage. ”

Listeners to Radio 4‘s The Archers will have heard the trauma of Jenny and Brian Aldridge having to visit a morgue to identify the body of what might have been their missing daughter Kate. But the corpse was someone else’s child and now, after several months missing, Kate has returned home. Advising script writers on the realism of story lines is something the Missing Persons Helpline is glad to do “because the effect can be that a family gets in touch who otherwise wouldn’t”, says Sophie Woodford.

The majority of missing cases are the result of passing anger - and the wish to punish parents - or sometimes simply thoughtlessness. The NCH Action for Children survey found that runaways were motivated not by the bright lights of a big city but by what they perceived was the awfulness of home. They ran as a result of family rows, and “often fundamental disagreements with parents over lifestyles”. Subjects of arguments included staying out late, offending, alcohol and drug abuse, truancy and other problems with school.

Most missing youngsters are found before their details reach the police. But the term covers a wide spectrum of circumstances. “If a child stays late somewhere, then turns up bright and breezy three hours later, were they actually missing?” says Derek Millar. “If parents have something to do with pushing the child away, is the child missing? Some run away from child abuse and the parents know it and won’t tell the authorities. Some spend more and more time with their grandparents, they sort of ‘fall away’. So you’ve got thrownaways, fallaways, runaways, all sorts of ways in which children can go. And we can only deal with the ones we’re told about. They’re not missing until they’re reported to us.”

Once a child has run away, he or she is fairly likely to do it again. The Children’s Society’s research into young people using their refuges found that most had run away many times and later running-away incidents were, on the whole, more extensive and wide-ranging than the first. But before the first “missing” there are rarely warning signs. “We have had cases,” says the head of pastoral care in an inner city girls’ school, “where pupils have said ‘if I’m made to go back home again, I’m going to run away’. If that happens, it’s usually a child protection issue and we would notify the appropriate social services. But usually we don’t know that things are going to happen. When you’ve got a large institution you can’t always pick up the signs straightaway. ”

Even when schools do fear such an incident, they may not be able to avert it. Another inner London school had a 13-year-old pupil go missing last year. “Leonie”, new in the school, came from a troubled background. Because she often went missing for a couple of days at a time staff had been working hard on her, says the deputy head. “Her head of year did lots of counselling. All our work had been in trying to make school a safe place, and some sort of security in her life. Our perspective was that if we could make it an important event in her life, she might keep attending.”

In the event, outside pressures proved stronger and Leonie disappeared in September last year. “Her mother phoned and said she was missing,” says the deputy. “I think there’s always a sense of disappointment when you realise that what you’ve been doing with a child hasn’t succeeded. But definitely the reason she disappeared wasn’t that she was unhappy at school. She was allowed to be a child in school, but her life was very different outside school.” Leonie turned up at the end of November, but has not returned to the school.

If a child goes missing it should be viewed “as a flag being waved”, says Inspector Millar. “Certainly we would be concerned if there were regular reports of a child going away from home - the same would apply if they were running from a children’s home. We encourage officers to visit when the child has returned to say ‘why did you go? Is everything all right?’ We’re not witch-hunting, but we all have a duty of care to the child.”

If problems at home are only moderate, running away can bring about some benefits. In the case of the Shenley Court School boy who ran away from home “the lad grew up quite a bit as a result of the experience”, says Keith Dennis. “I think really because he was engaged in the conversation about it afterwards.” A senior teacher in a girls’ school said that going missing was most common in Years 10 and 11. “That could well be to do with the restrictions that get placed on adolescents,” she says. “But often the parents do give in a little bit after the child has stopped out overnight, and they will see that their daughters need a bit more freedom than they’re getting.”

Whether the disappearance has been short or long term, going back to school is likely to be difficult. For Keith Dennis, this is where the school can come into its own. Even a very brief disappearance can, he says, arouse powerful feelings of guilt and anger in the parents, and distress in the child.

“The critical work really is when the youngster’s returned,” he says. “Our teacher counsellor plays a key mediating role in restoring things to a level, getting the youngster and the parent to the point where they’re actually talking to each other in a significant way. It seems to be successful in that I’ve not had a case where it’s happened more than once.”

Some of the posters of young people in the lobby of the Missing Persons Helpline have FOUND written over them. That means good news, they were found alive. A very few have LOCATED. That means bad news - found, but not alive. Janet Newman, co-founder of the Helpline, gives talks in schools about running away. “It’s terribly difficult to get them to recognise the dangers”, she says. “The nicest part about youth is that you don’t see danger.”

National Missing Person’s Helpline: 0500 700 700. Roebuck House, 284 Upper Richmond Road West, East Sheen, London SW14 7JE