A display of hand-drawn portraits outside a classroom is labelled, without irony: “Can you recognise your friend?” It’s a good question. It’s 10am on the third Monday of the new term at Northdown primary school in Margate, Kent, and headteacher Jackie Cox has just admitted 10 new pupils, aged between five and 11. In her office she scans the list. Four are from one family - Kosovan refugees with Birmingham accents; four children from two other families have enrolled from the women’s refuge nearby; another is a pupil who was at the school, then left, but has returned after a spell in Blackburn; the last is an eight-year-old, transferring from another local school.

Other headteachers might be left reeling, but for Jackie Cox and her staff at Northdown, this is normality. Less than three weeks since the start of the autumn term, 26 new children have joined the 280-pupil school - “with great big histories, every one of them”, says the head. Thirteen children expected back after the summer have yet to appear.

The rapid and casual movement of children in and out of Northdown - “There’s no finish in the same way that there’s no formal start,” says the head. “They just come and they just go” - defines much of the school’s culture and practice. It has only one class list - updated by hand throughout the week by the school secretary. Behaviour and anti-bullying policies - the vital handrail for these children in an unstable world - have to be constantly revisited as new children are absorbed. Planning and target-setting are impossible, and notions of shared history hollow. “We don’t take class photos,” says Jackie Cox. “It doesn’t have any meaning.”

Few schools in Britain have to provide the mixture of high-quality education and emergency social service that Jackie Cox and her staff give their children. This school is on the north Kent coast, a few miles from where Charles Dickens wrote Bleak House. And it is Dickens who comes repeatedly to mind, as the head talks of children arriving in the winter without socks, without underwear sometimes, without language or breakfast or basic social skills, their hair “moving” with lice. The chill words “pupil mobility” fail dismally to describe what happens in schools such as Northdown.

Jackie Cox calls her families “the itinerant poor”. They come from all parts of the British Isles, via refuges, rented rooms and other people’s floors, arriving sometimes with nothing more than the clothes they stand up in, having left behind trouble, debt and violence. In the playground, Kentish accents mingle with those from Newcastle, Glasgow and the West Country. Bullet-headed boys with eyes like old men’s and scabs on their foreheads chase each other around the perimeter then pull inhalers out of their pockets. Timorous girls approach the head for a hug. “It’s a happy school,” says Jackie Cox, “with some very unhappy children.”

Northdown primary stands in the middle of the run-down and unpopular Millmead estate in Cliftonville. Littered with sodden armchairs and crunched cars, the estate’s smaller housing units are used partly for temporary housing for families on the edge. A couple of miles away, behind Margate’s gaudy seafront, crumbling Georgian terraces have been turned into multi-occupancy, DSS-welcome flats, with cartons of milk and trainers on the flaking windowsills. Two refuges nearby shelter women and children fleeing domestic violence. Northdown - perennially with places to spare - recruits from all these places.

It is not pupil movement in itself that is the problem, says the head, it is mobility interlaced with the most extreme deprivation - and no outside recognition of the implications. Northdown’s newcomers struggle to cope, and by Friday the strain is showing. Tiny, fragile Luke, with peroxide hair and petrified eyes, screams at the top of his voice for a full hour-and-a-half before being persuaded into his Year 5 classroom. “Is he now expected to sit down and do literacy hour?” asks the head, rhetorically.

Two of this week’s other new children, it transpires, do not officially exist. They have moved so far and so often that no records can be traced. “Here we are with children we know nothing about,” says Jackie Cox, “except that they’re living in a refuge.” Only the Kosovan children, lovingly collected at the end of each day by their limping father, are relatively stable. “Arriving from a war zone in the back of a lorry seems to be less traumatic than the lives our indigenous children lead,” says Jackie Cox.

Despite everything, staff sustain a calm and focused atmosphere. Everywhere you look in the open-plan, mixed-age classes, children seem to be on task and engaged. Fourteen teachers plus the head are backed up by 17 learning support assistants. All appear to be giving their lifeblood. One - Alison Hatch - is a primary teacher of the year finalist in the National Teaching Awards, having already won the south-east regional award. Her classroom is an Aladdin’s cave, with a giant, silver-foil-clad St George and children’s hot-air balloons floating from the ceiling. Staff run after-school clubs in dance, art, football, music and gardening, and make opportunities all the time to affirm children. “Hello, Charlene! Still being brilliant?” says one. “We’d praise them for breathing if we had to,” says another.

Contrary to the indications of the league tables and its reputation locally, this is an excellent school. But as a recent report on pupil mobility makes clear, Northdown and schools like it struggle to manage the comings and goings of families, and the degree of associated trauma for children. High mobility (the DfEE calls 30 per cent and over “very high” - at Northdown it was 44 per cent last year) takes up staff time, affects the learning of all pupils and puts tremendous pressure on staff. “The task of managing the continuous movement and trying to raise the achievement of all is daunting,” the report, from researchers at University College London, concludes (Briefing, TES, September 15). But little allowance is made in policy-making, although Ofsted now takes mobility rates into account in its inspections, and, in future, primary league tables will discount the results of refugee children with less than two years’ schooling in Years 5 and 6.

Jackie Cox, who has been head for four years and was deputy for four years before that, believes her school is in an almost impossible situation. “We’re about teaching and learning, but you’re faced with these little scraps who are extremely needy,” she says. “Teachers have to do a real balancing act. They have to put in 200 per cent, even on an off day. There’s no such thing as sitting quietly in a corner hearing a couple of readers.”

While many of the more rooted local children also have social and educational needs, mobility makes all the difference, says the head. “Our local population are also often dysfunctional, but they’re known by the police and social services and you can have a multi-agency approach. The transient families just slip through all the nets, they miss out on pre-school experience, they have no health visitors or doctors. They get to school and their needs are noticed but they often don’t stay around long enough for statementing to take place.”

Northdown no longer accepts next-day admissions. To cope with the volume of newcomers, it has a system of showing families around the school on Wednesday afternoons, followed by an interview with the head the week after and admission the next Monday. This 10-day breathing space enables staff to contact previous schools for records and make plans for supporting each child. A rail of old uniform garments hangs in the parents’ room, to help dress the incomers.

Some admissions are also averted this way. “It gives us the opportunity to lose those people who turn up for two days and disappear,” says Jackie Cox. Two children enrolled after the start of this term have already vanished. The police are enquiring about them but staff don’t know where they are. “You don’t know they’ve gone until you get a request for records from another school.” Teachers have to live off their wits, enquiring from the taxi company that brought the child to school, or ringing the bloke who bought Dad’s mobile and asking if they’ve seen him in the pub.

Teachers such as key stage 2 co-ordinator Diana Buckley offer a practised and low-key welcome throughout the term. “There’s the constant challenge of having to assess new pupils,” she says. “And children who find themselves plonked in a new school aren’t immediately going to give their best.” Circle time is important, and the demands of the national curriculum sometimes have to make way for children’s urgent need to talk about what is happening to them. One child recently came to school after a car had crashed through his bedroom wall in the night. “He’s a bit tired,” said his mother, “but he’s better off here.” Staff attend up to four social services case conferences a week. One pupil is currently the subject of a care order for neglect after she and other younger children were found wriggling through a hatch into their mother’s locked kitchen to scavenge food.

A few families leave their problems behind and settle happily here. “Communication with teachers was marvellous,” says parent Tina Alexander, who arrived three years ago from the refuge and now lives locally with her two children. “They settled them in quickly. My son went from hiding under the table to hitting every child in sight, but now he’s fine.”

There are successes. And Jackie Cox, smart and humane in a smokey mauve suit and silver earrings, is passionate on behalf of her pupils. “We have to give children aspirations, offer them stability and let them know there is something better,” she says. “We have to have the same high aspirations for them as you would for any other children, because no one else is going to. They leave the horrors of the world outside and come in here to what we hope is a safe, warm, learning environment.”

But she and the staff are constantly smarting under the injustice of a system that treats Northdown like any other primary school. How can they be held to league-table account for the education of the child they admitted from the refuge two weeks before last summer’s SATs, who registered as “working towards” level 2 and left a week after the test? Or the loss of the children who staff worked intensively with for a year, whose mother turned up at school one afternoon with a suitcase and sleeping bags, and hauled them out to go to London. “The last we saw of them was walking down our path,” says the head. Even compared with supposedly similar schools, Northdown’s SATs results look poor. But mobility is left out of the equation.

And who is considering the effects on the other children, the children staff here call their “homegrowns”? A minority of pupils originate from the local area and remain there through their primary school years. Their friendships are fractured and their needs - less acute than the transient children’s - are repeatedly pushed to the back of the queue. “Something simple like dyslexia never gets to the top of the list,” says the head. She believes mobility levels at Northdown combined with the poverty of local and transient pupils combine to make it effectively a special school, in need of special school rates of funding and salaries.

More than 80 per cent of pupils are at levels 1, 2 or 3 of the code of practice, or have a statement. The remaining children all have some degree of social problems, says the head. Children are brought to school sick because parents believe they are better off there than at home. They vomit over staff, have diarrhoea, arrive in the knickers they wet the night before. Deeper and messier by far is their emotional condition. Mothers ring to say they are being threatened with murder; Ofsted inspectors were pelted with stones leaving the school after a late-night meeting.

“David Blunkett doesn’t know what poverty is,” says Jackie Cox. “He thinks it’s working-class families like mine was, with aspirations. We have a sub-culture here; the children are wild things and we have to try to make them normal.”

She believes the school could make a huge contribution to stabilising pupils’ lives and families, if the right model was put in place in Northdown and schools like it. Help with parenting, housing, benefits, adult education, health, debt and all the other issues families struggle with could be offered in a parent centre attached to the school, not, as currently, piecemeal by exhausted teachers. “My vision is to be able to welcome families into a base at the school,” says Jackie Cox. “I want them to feel school is too good a place to leave behind. We need a different model. I’ve been shouting for eight years but the issue isn’t addressed.”

Pupil Mobility in Schools, by Janet Dobson, Kirsty Henthorne and Zo Lynas, is available from the department of geography, UCL, London WC1H 0AP. Price pound;3.00 inc pamp;pJackie Cox can be contacted at: jcox@northdown23.freeserve.co.uk