The Coalition is planning to allow hundreds of secondary schools to control their own entry policies and Michael Gove warmly praised the system, which allocates places according to academic ability and reserves many places for children with the weakest performance.

“Fair-banding” admissions schemes are often seen as a way of breaking the middle-class dominance in the best-performing state secondaries since they prevent affluent parents from monopolising places by paying a premium to live in their catchment areas.

Banding generally means that 11 year-olds applying for school places sit an IQ-based “attainment test” and are then divided into seven or nine ability groups. The same number of children from each ability group are then given places at the school.

Advocates say that reserving some places for children with the lowest scores ensures that children from poorer homes are more likely to get places at the best schools. Critics say it unfairly discriminates against children with the best results.

The Conservatives have not previously spoken out in favour of the practice, but Mr Gove told the BBC that fair banding had “a role to play” and could make schools “truly socially comprehensive”. It prevented better-off parents boosting their children’s chances by buying homes near better schools.

“You can make sure that if your school is located in an area which may well be relatively privileged, by dint of house prices and background and so on, that you are spreading the load academically,” he said.

There is no official record of how many schools use fair banding, but a Daily Telegraph survey last year identified at least 22 local authority areas where the rules were in place.

The Schools Department estimates that only around 100 local authority-controlled secondary schools in England admit students on a fair-banding basis.

But almost half the 200 academies currently operating, which set their own admissions policies, are estimated to use some sort of fair-banding policy.

Mr Gove has claimed that hundreds of schools are considering opting out of council control under his plan to allow all schools to become academies. If that prediction is accurate, there could be a dramatic expansion in the use of banding policies.

Mr Gove praised schools including Dunraven School and Mossbourne Academy, in south and east London respectively, as high-performing schools that use banding.

Dunraven school in the south London borough of Lambeth introduced fair banding in 1992. It puts children in five different bands and gives priority to those children who are in care or in foster care.

David Boyle, the school principal, said results had improved dramatically since the system was introduced. The number of GCSEs at grade C or above had increased from 30 per cent in 1992 to 82 per cent this year.

He said that Dunraven was now more aspirational. “Our mission is to try to ensure a service for the whole community,” he added.

A source close to Mr Gove said: “We are not telling any school to use fair banding nor are we telling them not to. We want all parents to be able to send their children to a good school. That’s why we are expanding the number of academies.”

Some experts say the schools with the greatest incentive to adopt banding are those in the poorest areas, because they often struggle to attract brighter children.

But supporters of the policy say all schools can benefit from becoming more socially and academically inclusive.

The charity Barnardo’s this week called for the widespread use of fair banding. But David Green, the director of the think tank Civitas, described it as “a kind of social engineering based on animosity to middle-class parents.”

Prof Stephen Gorard from Birmingham University warned that Mr Gove’s voluntary approach to admissions had risks. “If banding is implemented partially and voluntarily, it sounds like the outcome will be all pain and no gain.”

John Bangs of the National Union of Teachers said banding was right in principle, but should be implemented uniformly. “Banding only works if you do it in a geographical area,” he added. “If every school has its own admissions policy and sets its own banding system, you’re going to get real unevenness.”

Nick Seaton, of the Campaign for Real Education, attacked fair banding as an unfair policy that denied places to the brightest. He added: “I’m not saying we shouldn’t help the worse-off, but it I don’t think the best way to do that is to disadvantage the better-off.” --By James Kirkup, 27 Aug 2010