Research by the Children’s Society found that more than half of parents are prepared to move home or lie to get their child into a “good” state school. What they mean by good was unclear, but for many it can be well above average results, an excellent Ofsted report and, ideally, a substantial middle-class intake.

However, other recent research funded by the Economic and Social Research Council has revealed parents may be unnecessarily fearful of their local comprehensive school.

Academics found that many children of middle-class professional parents who had gone to average or below-average achieving comprehensives got more personal attention from teachers eager to improve the school’s results. And sometimes A-level courses were kept going, despite high costs per pupil, so they could study their chosen subjects.

Most of these children performed very well and achieved very high marks in GCSEs and A-levels. And 15 per cent - higher than would be expected - went on to Oxbridge.

“Schools want to hold on to these pupils and so they get very favourable treatment,” said David James, professor of education at the University of the West of England and one of the authors of Identities, Educational Choice and the White Urban Middle Classes.

“We interviewed 125 sets of parents in three cities and many said it was happening. They said their children stand out and so they get attention.” He said that most had also been scooped up by schools’ gifted and talented programmes.

Professor James added: “The way schooling works actually underlines the advantages they already have.”

Although the middle-class children excelled academically, the researchers found that they did not mix well with working-class children, preferring to seek out others with a similar socio-economic background. This situation was exacerbated by streaming and setting.

Some of these findings may please the Government, which would like more middle-class parents to opt for their local comprehensive. That potentially could reduce the number of low-achieving schools, but it would not necessarily improve the standard of education on offer.

Ministers also want to make sure middle-class dominated schools with good results are open to all - not just those who can afford a home in the area. A free transport plan was announced last summer to allow working-class pupils to attend schools miles from home.

Last November, Trevor Phillips, chairman of the Equality and Human Rights Commission, said high-performing schools should consider limiting places for middle-class pupils, to make room for those from poorer homes. He cited examples in North Carolina, where a policy of mixing pupils by race had been abandoned in favour of mixing by socio-economic class, using free school meals entitlement as a marker of poverty.

“Addressing class difference is critical to our ambition to challenge the iron law that an infant’s start in life would be conditioned by who his or her parents were,” he said, “and here we could be really radical.”

Ed Balls, the Children, Schools and Families Secretary, seems set on using admissions rules to better balance intakes. The Education and Skills Act, passed last week, makes it easier for the Schools Adjudicator to challenge schools’ admissions arrangements. The new code obliges schools to make their uniforms affordable, and forbids interviewing parents before offering places.

But the changes do not tackle the effects of catchment areas, which potentially allow parents to buy their way into a more popular school.

Dennis Richards, headteacher of St Aidan’s High in Harrogate, said schools faced conflicting pressures. The admissions code seemed designed to stop schools taking more middle-class intakes, but if they accepted more disadvantaged pupils, they risked a drop in their results.

“Government policies are in direct conflict, as league tables mean it may not be in headteachers’ interests to take that risk,” he said.