Dr Stephen Gorard, professor of social sciences at Cardiff University, said new evidence showed such schools had a “privileged” intake and that their catchment areas were more segregated socially and economically. “They are acting against social mobility,” he said. Policy-makers would have to weigh up the advantages of these schools with the risk that they could lead to a more segregated school system.

Dr Gorard and Dr John Fitz carried out the study, Investigating the Determinants of Segregation between Schools, as part of wider research on school choice. Their overall study looks at how the school system has changed since the 1988 Education Reform Act gave families the right to express a preference for any school they want. The researchers are analysing information onaround 8 million pupils from 25,000 schools in England and Wales over the past 12 years.

Dr Gorard is due to present the new study on June 11 at an Institute for Public Policy Research seminar in London on “How Special are Specialist Schools?” The IPPR seminar will explore the implications of two proposals - one in the recent Department for Education and Employment Green Paper to increase the number of specialist schools from 538 to 1,500, and another in the Labour party manifesto to allow all secondary schools to develop a specialism.

Dr Gorard added that his study showed that, in general, LEAs with a higher proportion of foundation, selective or specialist schools had higher “levels of socio-economic stratification between schools”.

The findings contrast with Dr Gorard’s earlier research on school choice, which showed that overall segregation between schools had been declining since 1988.