Ofsted stepped up its drive for higher school standards this week as its chief inspector said mixed-ability classes could be a "curse" on pupil progress, told heads to make better use of their funding and warned against early GCSE entry.
Sir Michael Wilshaw's comments prompted heads' leaders to accuse him of trying to "micromanage" schools. But the chief inspector of schools - who this term introduced a tougher inspection regime abolishing the "satisfactory" grade and giving schools four years to become "good" - is determined to increase the pressure.
He also suggested that the vast increase in teaching assistants over the past decade had not made the best use of schools' money and said he was surprised by Ofsted research showing that nine out of 10 heads said that the extra pupil premium funding had not changed the way they worked.
Sir Michael, who took up his post in January, said he wanted schools to do more to ensure that more pupils fulfilled their potential. About 20 per cent of pupils who left primary with higher than expected level 5 results did not achieve top A*, A and B grades at GCSE, he said. They were being held back by low expectations, insufficient tracking of progress and "the curse of mixed-ability classes without mixed-ability teaching".
"Where there are mixed-ability classes, unless there is differentiated teaching... it doesn't work," he said, adding that effective differentiated teaching was "hugely difficult" to achieve.
He said mixed-ability classes could be an "article of faith" for schools who were not concerned enough about good practice and were doing something "more akin to social engineering". In those cases Ofsted inspections would be "very critical".
Sir Michael said the recent growth in early GCSE entries was also holding back able pupils. Ofsted figures from 2011 show the impact by comparing the English GCSE grades of pupils who were "high achievers" in primaries. Only 37 per cent of those entered early ended up with an A* or A grade, compared with 49 per cent of those who left exams until the summer of Year 11.
"We think early entry hurts the chances of the most able children," Sir Michael said. Ofsted would be critical of schools using the tactic except where they were "absolutely confident that youngsters are reaching their full potential".
On the pupil premium, Sir Michael said: "It is simply not good enough for heads and schools to say it is not changing policy."
Brian Lightman, general secretary of the Association of School and College Leaders, said Sir Michael should not be "micromanaging" schools. "It is a fundamental principle of inspection that it should be focused on outcomes and I am surprised to hear the chief inspector advocating particular approaches," he said.