A marked increase in the number of supersize secondary schools has led to an erosion of discipline, as teachers try to keep control of children they cannot identify even by year group, let alone by name, research suggests.

Expulsions from the largest secondaries, with 1,500 or more pupils, have risen by 28 per cent since Labour came to power in 1997, leaving 730 pupils a year permanently excluded from school. Temporary exclusions are now running at nearly 10 per cent of pupils in schools with more than 1,000 children, compared with 3 per cent in schools with 1,000 or fewer pupils.

David Willetts, the Shadow Education Secretary, obtained the figures as the result of a parliamentary question. He said the problem was not to do with class size, but with the creation of giant, anonymous institutions. “Maintaining discipline is now becoming very difficult in the biggest schools. This is partly because the pupils and teachers in a large establishment are anonymous to each other, making it difficult for staff to tell pupils off and follow up with the appropriate action. If head teachers don’t know who all their pupils are, it becomes difficult for them to identify the ones who may cause problems and to intervene early to stop these from escalating,” he said.

His comments come after a report last year from the schools watchdog, Ofsted, which found that schools with the most discipline problems were the ones that were unable to detect and deal with potential troublemakers early. Ofsted also noted that schools where teachers did not get to know their individual pupils well, because of high staff turnover, tended to have the biggest problems tackling poor behaviour.

Mr Willetts said the emergence of a new breed of giant comprehensive had been achieved by stealth. Since 1997 the number of secondaries with more than 1,500 pupils has more than doubled to 315. The number of secondaries with 1,000 or fewer pupils has dropped by a fifth to 2,119.

“Partly by accident and partly by design, we have created powerful incentives for schools to get bigger and bigger. Students now do a wider range of subjects and schools need to be bigger, with bigger staffs, if they are to offer the full range now expected of them. Also, the way capital is allocated to schools means that it often makes more sense for local authorities to sell off one school site and rebuild others,” he said. The doctrine of parental choice had also led to the expansion of the most popular schools. A more considered approach towards school size was needed, Mr Willetts said, before discipline problems spiralled out of control.

Chris Keats, the general secretary of the National Association of Schoolmasters and Union of Women Teachers, said it was simplistic to equate large schools with poor discipline, but accepted that the biggest schools did face particular issues with behaviour. “If you have a large school, you have to put in smaller units, such as year groups, or upper and lower schools, to make sure that the teachers know the pupils they are dealing with.”

A spokesman for the Department for Education said: “Large schools can of course face additional challenges, but with strong leadership and good staff they can also use their size to benefit their pupils and the wider community by offering out-of-hours clubs and community facilities.”

He added that the expansion of the most successful and popular schools was part of the Government’s commitment to increasing choice and diversity.

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