What's it like to start a new school in a new country? Eleven-year-old Jassima has a pretty good idea.
She's been helping Majeda, newly arrived from Bangladesh, settle into Cleveland junior school in Redbridge, east London.
"It must be weird," she says. "All the people around her were talking different languages and she didn't really know what was going on."
Jassima - and fellow pupils Cintya and Sophia Laouia - are old hands at this. They are practised "language buddies" to other pupils, and have learned that no one likes to face a difficult situation alone. In Redbridge, it is a lesson that has also been learnt by schools.
The number of pupils who join or leave a school during the year is increasingly recognised as an issue for urban schools. Late last year, ministers issued guidance to help schools ease the disruption caused when new faces arrive mid-term.
But Redbridge schools have gone a step further, working together to tackle some of the root causes, starting with their borough's housing and school admissions policies.
Heads formed a working party when they noticed a sudden increase in the problem in the late 1990s. That later became one of five networked learning communities (NLCs), set up by heads after a poor local education authority inspection in 2000.
NLCs are an initiative of the National College for School Leadership, designed to promote collaboration and research - some 130 now exist around the country. Redbridge's are co-funded by the college and the council and co-led by heads and LEA advisers.
Networking is the Government's new big idea for school improvement. But it is usually seen in terms of mutual support and spreading good practice. In Redbridge, it demonstrates something else: the benefits of strength in numbers.
It also reflects a role school leaders may increasingly find themselves in as the implications of the new Children Bill are felt. For many heads, close collaboration with other agencies is about to become a way of life.
Pat Ward, head of Cleveland junior school and co-leader of Redbridge's mobility network, outlines the extent of the problem: in 20023, 20 of the borough's 50 primaries saw more than a fifth of their pupils join or leave during the year -the Government's definition of high mobility.
In all but eight it was more than 10 per cent, and in one school it topped 68 per cent. At Mrs Ward's school, more than 100 children came or went during the year.
The borough has large numbers of families from ethnic minorities, and of refugees, but research suggests the problem extends beyond asylum-seekers.
There are also large numbers of pupils moving between schools.
Initially, the network focused on mitigating the impact of so many unscheduled arrivals. They developed quicker assessment of new pupils, smoother induction, and peer support schemes like the language buddies. A guide will be published shortly.
But network leaders realised that collectively they had the means to research the roots of mobility; to investigate which families were most at risk, and the practices that contributed to children moving. And they realised they had a voice.
Research found some of the most mobile families were migrants placed in short-term accommodation, moving from address to address every few weeks.
Loopholes in housing law mean landlords do not have to maintain short-let properties so well, so vulnerable families get shunted around.
"It's the nasty end of the market," Mrs Ward says. "Housing in this area hadn't really thought about the implications of what happens when you keep moving a family and the fact their children might have to keep changing school."
The network developed contacts with the housing department and Mrs Ward believes officials are now more aware of the disruption they can cause pupils' education - although she says: "I wish I could say we're able to wave a magic wand."
Meanwhile, a shortage of places in some schools meant the local authority schools admissions department would sometimes place the children of asylum-seekers or other newly-arrived families in three or even four different schools. As the parents became more settled, they would then move their children into one school.
Admissions officials now try harder to place children together, but Mrs Ward says: "I still have families with children in two or even three schools. If you don't drive, that's very difficult."
The LEA also gives schools more information about the pupils they are receiving -data such as residency status or home language.
"We used to have to track asylum papers or passports," says Mrs Ward.
"Parents would do it once when they registered with the education office, and then we'd have to do it again." It is, she says, the kind of information parents with very little English have problems repeating, "and it got us off on the wrong foot with parents".
Those changes have eased the administrative burden on schools and smoothed the passage for new pupils. "The more information you have at the beginning, the quicker you can have the right sort of interpreter and the right support for the family."
Vicky Coxon, the senior LEA adviser who co-leads the five Redbridge networks, says it is a huge benefit to have "high calibre people - heads and teachers - who are experiencing mobility and working on it together, finding out why it's happening and what we can do, as an authority, to reduce it."
There is a risk, she agrees, that LEA policies in areas such as admissions can contribute to mobility. Statutory constraints such as infant class size limits make it a difficult problem to unpick, but the council's funding and co-leadership of the network showed it was a high priority.
"The fact we've got a network means it stays at the forefront of people's minds," she says.
The next phase will be further research. Heads want to start making links with the ethnic groups most affected; they are already working with the Somali community on pupil achievement in response to a request from its leaders. But surprisingly little information exists on the ethnic background of mobile pupils. "These are the kinds of thing that a school just doesn't have time to analyse," says Mrs Ward. "But as a network, we can. We've been able to go beyond spreading good practice to taking action."