In February, Mr Miliband pledged to monitor results in 30 specialist schools which have abandoned time off for revision. He said that a laissez-faire approach to revision seemed particularly damaging to boys and pupils from the poorest backgrounds. "It is the next level of GCSE performance that counts, not the next level on the games console," Mr Miliband said.
His views have been inspired by the experience of Kemnal technology college from Sidcup in Kent which scrapped leave two years ago and even asks pupils to attend lessons on mornings before exams.
John Atkins, the headteacher, says this alone has improved GCSE results, by up to 10 per cent. The proportion of boys gaining five A-C grades soared from 7 per cent in 1990 to more than 50 per cent last year. The school brought in extra support staff to invigilate in exams while teaching assistants helped to supervise.
Mr Atkins said: "Not all the boys liked it, but afterwards they told teachers it was one of the best things they had ever done."