Transience and mobility - the effect that interrupted and changing schooling has on teachers, pupils and families alike - is one of the unsung major issues that has to be addressed now if there is not to be a hole in the strategy for raising standards.
Across government, the watchword is joined-up thinking, and targeted policies, including employment and health action zones, are recognising that the fight against social exclusion needs co-ordinated action. But the mobility factor - at least in education - is curiously unploughed ground.
Children who attend several schools in the course of their education self-evidently are interrupted in the continuity and the balance of their learning experience. But it's perhaps been less recognised that many such children are already disadvantaged by the circumstances which led to their mobility in the first place.
Why do families move? Sometimes to get a better job, yes, but often to get any work, however low-paid, temporary or insecure. Sometimes to escape broken homes, drug problems in rundown estates, poor accommodation (often moving into no better) or getting away from abusive or threatening relationships.
The children affected and moved - with or without their families - have educational disruption added to personal and social traumas. And for the schools that take them, despite often sterling efforts by dedicated staff, their arrivals and departures have a disruptive effect on resources and standards.
Anecdotally, much of this has been known for some time; certainly as an MP for a seaside town with annual influxes of people - often with young families - seeking seasonal employment, I have been well aware of it.
As the head of one of the most "mobile" primary schools in Blackpool put it, "large numbers of pupils moving in and out makes target-setting and tracking pupils' progress extremely difficult".
But now the evidence is beginning to come out. Details provided to me by the Department for Education and Employment on those local authorities which have highlighted turnover in pupil enrolments in their educational development plans show where the problems lie:
* inner-city areas, particularly London boroughs, with short-term housing and transient groups such as travellers and refugeesasylum seekers;
* old manufacturing areas, deprived neighbourhoods and out-of-town estates suffering from population drift and people leaving permanently, and;
* seaside areas, where the seasonal demands of the tourist industry linked to poor quality housing exacerbate the problem.
The result - as the east London borough of Hackney puts it - is that transience and mobility "make it more difficult to predict needs, to target interventions appropriately and to measure accurately progress".
The scale of the challenge - especially in the crucial early years - is alarming. Blackpool, for example, took 1,174 pupils into its primary schools in 1997-98 as non-routine admissions - 14 per cent of all its primary pupils.
Figures for single schools are even starker: one Blackpool primary had a 48 per cent turnover of pupils on the roll; in others a mobility factor of 20-25 per cent is common. East Yorkshire, Tower Hamlets, Barnet, Wiltshire and Cambridgeshire, among others, have similar problems.
Further evidence is expected to come from DFEE-backed research by the migration unit at University College London, which began in January.
Preliminary results are expected to reinforce the message of the development plans - but will also point out the smoother transition for pupils from higher-income families where better planning, family support and better-resourced schools ease the path. The virtuousvicious circle of haves and have-nots once again affect education and life chances.
To date much of what has been done to address these major problems has been local and not recognised or funded by government. This is beginning to change. MPs have recommended that the inspection framework should take account of mobility's effects on school performance - and that the DFEE records such levels annually. I'm delighted that the minister, Estelle Morris, replying to the Commons debate on OFSTED with the Government's response, indicated that this will now be done.
Many of the new education action zones will have problems with high pupil mobility. They should be used as test-beds to evaluate new approaches to meeting the needs of transient pupils and families. Areas such as Calderdale, Leicester and Newham - all with mobility problems - could be starters.
What should be tried out? Blackpool recently floated the idea of an "integration support service" - developing the personal and social skills of children and encouraging parents to support their children. These need buttressing with projects such as breakfast clubs and family literacy centres.
And the Government needs to make hard-edged decisions - taking account of pupil mobility in calculating councils' funding as it does with other deprivation indicators that are linked to performance.
Some of these needs will begin to be met by government initiatives such as Excellence in Cities. But just as Sure Start is yoking together the educational and social needs of pre-school children, so we need co-ordinated action on mobility and transience in our schools now.
Gordon Marsden is Labour MP for Blackpool South and a member of the Commons education select committee