Wellington College and Guildford High School are among 150 new teaching schools accredited by the National College for School Leadership.

BBC: Private schools to train state school teachers

But the schools minister has announced plans to make the qualification voluntary - promoting autonomy rather than regulation - and to have the content of the training revised by the National College for School Leadership.

BBC: Heads qualification will no longer be compulsory

Sir Michael told the annual conference of the National College for School Leadership in Birmingham that he recognised there had been big improvements in areas such as London, and among some ethnic minority groups, in recent years.

BBC: Ofsted to review educational achievement in poor areas