An explosion in the number of supersize schools with 1,500-plus pupils has led to a decline in classroom discipline and limited academic achievement, new research suggests.

Pupils in schools catering for more than 1,000 children are nearly three times more likely to be excluded than those in smaller establishments. There is also evidence that children in smaller schools are performing better academically — only 38 per cent of secondaries in England have fewer than 1,000 pupils, yet these include eight of the ten top state schools.

Analysis of government data by the Conservatives follows research from the charity Human Scale Education, which suggested that students behaved better and achieved more in smaller settings. The charity is now advocating the approach of some American education authorities, which are breaking down giant comprehensives into smaller units sharing a single site.

Since 1997, the number of secondary schools in England with more than 1,000 pupils has risen by a quarter to 1,580, while those with fewer has dropped by a similar proportion to 1,841. Nearly one pupil in seven is now educated in a school with more than 1,500 students, and 47,540 children attend schools of more than 2,000 — three times as many as a decade ago.

Teach First, which recruits high-flying graduates to inner-city schools, claimed last year that supersize comprehensives could result in pupils failing to build up relationships with staff.

Michael Gove, the Shadow Children’s Secretary, said that teachers were struggling to keep control of students they could not identify even by year group, let alone by name. “All the evidence is that some of the toughest problems with discipline are found in the larger schools. The Government’s pile-’em-high approach is letting down the most disadvantaged pupils.”

The advance of giant comprehensives has been fuelled by the expansion of the curriculum, which means that schools need to employ more specialist teachers to cover a wider range of subjects. The way capital is allocated to schools also means that it often makes more sense for local authorities to sell off one school site and rebuild others.

Lord Adonis, the Schools Minister, rejected the Tory claims about indiscipline and said that schools were increasing in size because parents and children wanted them. He said. “They [the Tories] are comparing large secondary schools with all other schools, including primary schools, which almost always have lower exclusion rates than secondary schools.”

Steve Sinnott, the general secretary of the National Union of Teachers, said that it was simplistic to equate large schools with poor discipline, but added that the optimum size for a secondary school was probably 800 to 1,000 pupils.

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