HIGH levels of pupil turnover are hampering the Government's attempts to raise school standards in some of the poorest parts of the country.
A Government-backed study concludes that schools struggling to educate some of the most deprived children are also having to cope with a huge turnover of pupils.
Some schools can see as many as 100 children come and go in a year and between a quarter and a half of schools in parts of London and other urban areas can have pupil mobility rates (the proportion leaving and being replaced by others) above 20 per cent.
The research by University College London academics reveals that pupils who join school at times other than the normal starting age tend to do less well in key stage tests and GCSEs.
But the study, which will be published next week, says that the lower levels of performance generally appear to be linked to factors such as social deprivation and whether children have English as a second language rather than disruptions caused by changing school.
This was backed up by Steve Strand of NFER Nelson who analysed the progress of 6,000 pupils in an English urban authority's comparing their baseline assessment results at age four with the key stage 1 results.
Dr Strand found that poor performance was more likely to have been caused by the underlying reason for pupils' change of school rather than the move itself.
The UCL team says it now makes little sense to set targets for two years ahead for schools whee there is a high rate of pupil movement.
"Performance tables which do not reflect the real achievements of high mobility schools cause constant demoralisation of teachers working under extreme pressures," they add.
The 18-month study by Janet Dobson, Kirsty Henthorne and Zoe Lynas of UCL's migration research unit was largely funded, by the Nuffield Foundation and the Department for Education and Employment.
It says that children often change school because they are refugees, travellers, their families have broken up, they have been permanently excluded or they are in care.
But not all the children studied were disadvantaged. Some were from middle-class families whose parents had moved to pursue promotion or a change of career - and not all were low-achievers.
One school in the study identified high-performers among those who started mid-term, saying they had army ambitious parents who made the most of opportunities.
Dr Dobson said: "The Government needs to recognise that pupil mobility is an issue, that it is a shared responsibility and to give schools as much support as possible.
"There are financial implications and there are questions about making sure that improvement strategies support these schools."
Schools with high pupil turn-
over tend to be community or local-authority-run schools. Some are Church of England foundations, a few are Catholic.
Dr Dobson added: "We recognise that some schools do manage better than others and it's not an excuse for bad management or bad teaching. We need to spread good practice."