Jean Hickman, head of the Walsall Academy in Bloxwich, called for all schools to be given the same freedoms as her academy for setting teachers’ pay and conditions.

Mrs Hickman told the Commons’ education select committee that her pupils received up to 10 hours more lessons a week, which helped them improve exam results.

“It enables me to have longer teaching sessions. Children get up to 35 hours a week, as opposed to 25,” she said. The academy, opened in 2003, is jointly sponsored by the Mercers’ Company of London and Thomas Telford School in Shropshire, one of England’s best-performing state schools.

Mrs Hickman added that although staff are contracted to work from 8.15am to 5.15pm, they receive 20 per cent non-contact time, meaning they do not have to take work home with them.

Her comments followed a report published this week by the think tank Reform, which also called for the freedoms enjoyed by academies to be extended to all schools.

The report, written by Richard Tice, chair of governors at Northampton Academy, said teachers’ unions had become too powerful and were contributing to low teaching standards.

National pay deals have caused unions to become the blockers of reform, rather than organisations that supporting teachers in doing a good job, Mr Tice writes. It should be made easier for schools to sack weak teachers, a process that can take years at present.

Steve Sinnott, general secretary of the National Union of Teachers, described the findings as “mindless and offensive”.

Mary Bousted, general secretary of the Association of Teachers and Lecturers, said that there was already “huge flexibility” for schools in the national pay system.

www.reform.co.uk.