Ruth Lupton of the Centre for Analysis of Social Exclusion at the London School of Economics has found that, of 180 schools deemed “failing” in 19992000, just 19 were relatively affluent, ie in the wealthier half of the nation’s areas. Half the others drew their pupils from deprived areas.

All-boys’ schools were twice as likely to be in special measures, as were secondary moderns. No all-girls’ schools were failing.

Ms Lupton said that the findings showed that Ofsted needed to take greater steps to place schools’ achievements in context before judging them to be “failing”.

“The inspectors describe the context of a school at the start of their reports, but they don’t go on to look at what impact it has,” she said.

An Ofsted spokeswoman insisted that it uses a wide range of contextual information in its judgments. But she added: “Deprivation must not be an excuse for unsatisfactory provision. Subsequent reports on schools that have been through special measures show just what can be done even in the most difficult circumstances.”

In his speech to mark Ofsted’s 10th anniversary, Education Secretary Charles Clarke said inspectors should take a school’s broader context into account and acknowledge the work they did with other agencies tackling issues such as anti-social behaviour, drug abuse and teen pregnancies.