Of the 1.03 million school-age children being educated in the 33 boroughs, more than 145,000 are shunning schools in the authority where they live (see chart, left).

In all, 138,557 of those attend schools in other London boroughs, leaving the capital with a net loss of 6,566 pupils. These “missing” children tend to be educated in neighbouring counties such as Surrey, Hertfordshire, Essex and Kent, or in private schools.

The figures were compiled by the Greater London Authority. They do not include statistics for independent schools.

It is estimated there are more than 90,000 pupils being educated in private schools in London, although many of those will come from outside the capital.

The biggest “exporter” of pupils is Lambeth, which loses 10,966 children to schools in neighbouring authorities and takes in just 3,563, leaving it with a net loss of 7,403 youngsters.

Only 67.7 per cent of its resident children are educated in local schools, the lowest proportion of any London borough.

The highest retainer of pupils is Tower Hamlets (see box, left), which hangs on to 95.7 per cent. The borough, among the five most socially deprived areas in the country, exports 1,401 pupils and imports 2,547, leaving it with a net gain of 1,146 children.

Newham is the next most successful borough at keeping its children, on 93.4 per cent.

Westminster, also part of inner London, is the biggest winner in attracting children from elsewhere. The LEA shows a net gain of more than 3,500 pupils, followed by Wandsworth on just over 2,900. Malcolm Grimston, Wandsworth cabinet member for education, said a large influx of children from other boroughs could bring problems, especially at the transfer from primary to secondary education.

He said: “This level of movement brings its own challenges particularly when youngsters are coming from primary schools in their boroughs which do not match the standards of our local schools.”

In outer London, Brent retains the lowest proportion of pupils - 80.2 per cent. Although more than 4,600 come into the borough every day, almost 8,000 leave, giving it a net loss of 3,172 pupils.

Other low retainers of pupils are Merton on 81 per cent, Harrow 82 per cent and Greenwich, 83.6 per cent.

The best performer in terms of retention and net gain in outer London is Bromley. While more than 3,000 pupils travel outside its borders every day, it attracts 6,582 from neighbouring authorities. Overall, 92.5 per cent of pupils who live in Bromley attend one of its schools.

Following close behind is Redbridge on 92.1 per cent and Havering 92 per cent.

However, the movement of pupils around London is not necessarily down to parents’ choice.

A separate report into secondary admissions in the capital found that some authorities use criteria which effectively allowed schools to select certain groups of children.

The study by the Research and Information on State Education Trust and the London School of Economics, found that 13 per cent of secondary schools in the capital gave priority to children of LEA employees and governors, even though this may contravene legislation.

One in 10 gave preference to the children of former pupils, while 27 per cent had criteria relating to religion.

The report was particularly critical of voluntary-aided schools. Almost half - 47 per cent - used interviews as part of the selection criteria, a practice that will become unlawful in 2005.

The study concluded that the opportunities for overt and covert selection are greater in London than anywhere else in England.

The RISE report can be found on www.risetrust.org.uklondon