Old bonds can be hard to break. Most children moving on to a new class or new school this week have been looking forward to the change. But for some, a new start in a different culture can leave them hankering after the past.
If their old school has offered security, happiness, friendship, opportunities, the next step can be one step too far. Like boomerangs, they come back.
Steve Morrison, head of Kingsdale secondary in Dulwich, south London, tells of a pupil who moved with his parents to Birmingham for the start of a new school year. Except that after a while he seemed to be back, appearing at random. The first couple of times he was seen, staff couldn't believe it was him. Then came the call from the police. The boy had run away from home and his parents had alerted authorities that he was likely to return to his old school; to the place where his friends were, where there were familiar adults. "He had even lovingly ironed his school uniform and paid for his lunch," says Mr Morrison. "When I did manage to catch him I joked that his attendance was better than when he'd been a pupil with us - he had been quite a challenging child. We work hard at achieving good, positive relationships here between pupils and staff, we don't like to give up on children and if you have a healthy relationship with a challenging child they will appreciate that when they leave. The boy was returned to Birmingham, but managed to find his way back to us a couple more times after that."
Raj Persaud, consultant psychiatrist at the Maudsley Hospital in south London, says that the stability offered by good schools becomes a rare commodity in a rapidly changing world and that former pupils often feel nostalgic for it. "The rules and rewards for achievement are evident and the support of teachers engenders a sense of belonging that is rarely experienced again in life. That sense of acceptance is powerful and some people need to return to it at different stages of their lives."
For children moving from primary to secondary, the change in culture is immense and can be overwhelming. Often last year's Year 6 will pitch up back at their old schools during the first weeks to show off their uniforms and let their old, familiar teachers know how they're doing. But occasionally the sense of dislocation runs deeper and they return hurt and bewildered.
Fai Anderson, 13, an ex-pupil of Comber Grove primary in Camberwell, south London, was a high achiever, reaching level 5s in her English and science key stage 2 Sats. But secondary proved a different story. She became homesick at boarding school and within months began to lose weight and self-harm. By Christmas she was asked to leave and failed to settle at a subsequent state secondary. One day she turned up out of the blue at her old primary on the pretext of bringing a skirt that might fit a younger child - and ended up staying. "I went to see my favourite teacher, the one I'd had in Years 3 and 5. I just wanted to talk to her and she said I could come back and help with reading. I have quite a lot of patience with the little ones and it reminds me how much I loved it here."
Fai found the boundaries of behaviour and expectations of achievement less clear at secondary school. "I was pushing and pushing over behaviour. I know I shouldn't have been, but I felt I was spinning out of control."
Under the current arrangement Fai comes into Comber Grove one or two days a week while also attending a referral unit. Head Mike Kent says the school is "very matter of fact with her. She relates well to the younger children, especially those with difficulties. We are trying to show her that she has a lot going for her; that she shouldn't throw it all away. We're doing our bit to get her back on track."
Even children who have been permanently excluded from school will sometimes show up, hanging around school gates or in the grounds during break times.
Steve Morrison says they come back to the place where their friends are, "where there are adults they got on with. Even if they have been very difficult, there may be a dinner lady, mentor, teacher that they related to."
Excluded children will even hang around in their old school uniforms. They will do it to blend in, to keep that sense of belonging, or because they are the best clothes they have. "We've been asked by residents before now to get rid of students causing a nuisance in the neighbourhood. Our reply has to be 'we did get rid of them, and that's why they are troubling you',"
says Mr Morrison.
"We try our hardest not to exclude children because we like to negotiate with them from a position of strength, when they are still with us and we can exert some influence. Once they are out permanently they are beyond our control. It can take up to six months to place a child in a school elsewhere after they have been excluded, and being home alone if siblings are coming to school may be no fun."
He says he sometimes tries to talk to such children to stem any further aggravation. If that fails it can mean resorting to an ASBO (anti-social behaviour order), which is time-consuming.
John Dunford, general secretary of the Association of School and College Leaders, says that even when they are old enough to leave school, former pupils can cause a major problem by continuing to hang around the school grounds. "This is a particular issue in areas of high youth unemployment when young people have time on their hands. Sometimes a quiet word with parents and the young people themselves will resolve the issue. Sometimes schools have to turn to the police."
Raj Persaud says that school is a place where teenagers are able to get adult attention if nothing else. It is a place where people know their name and where the rewards for effort are obvious and transparent. Finding a way through life outside school is never as straightforward.
Doncaster's Campsmount technology college, which has a strong drama department, provokes passionate loyalty from former pupils. Ryan Greaves, who is now in his second year studying drama at university, returns regularly to attend the school's many theatre trips and drama workshops, to lend a helping hand and to gain from the experience himself. Ryan is from an ex-mining village, his father a former pit surveyor. The school, he says, provides rich, exciting cultural experiences in an area where there are none. Moreover, staff support and encourage students to an extent never replicated at college. "You don't have the same contact with staff as you do at school," he says. "At school we were constantly challenged and pushed to achieve beyond our reach. There was a real sense of daring in the drama department. We would put on shows for the sheer joy of it and everybody in the community would attend. You don't realise how much it gives to you until you leave. I miss that real sense of belonging. Staff at college are much more remote."
Independent schools in particular benefit from the loyalty of former pupils. Duncan Goodhew, the Olympic gold swimmer, for example, has returned to Millfield, his former school in Somerset, to increase funds available for scholarships and bursaries through the Millfield Foundation. He has also put his own children into the school. Millfield, he says, sealed his success: "They took me on when I was bald (he lost his hair when he was 10) and dyslexic and my self-esteem was at rock bottom. They spotted my dyslexia and my potential as a swimmer almost straight away and built me up from there. Without Millfield I wouldn't have won a gold medal, but it was only years after I left that I fully realised my indebtedness to the place."