The 67 London schools told to improve or be taken over

Ministers are unveiling plans aimed at slashing the number of schools where fewer than 30 per cent of pupils achieve at least five C-grades at GCSE, including English and maths.

Education watchdog Ofsted has warned that the drive to improve results has "stalled".

Some 67 of these 638 "National Challenge" schools - including 12 academies - are in London, but today the Government's chief school improvement adviser told the Evening Standard it would probably be impossible to reduce the total to zero, given the difficulties some had to face.

Sir Mike Tomlinson, who has been appointed chairman of the new National Challenge advisers' panel, said: "There will always be the possibility for some that this is a difficult, if not impossible, target - but that is not something that should stop things from going forward."

Schools Secretary Ed Balls has expanded the London Challenge, the programme for raising achievement in the capital's poorly performing schools to which Sir Mike is already the chief adviser, to cover the whole country.

Mr Balls warned that schools which fail to make progress towards the 30 per cent target could be turned into city academies, forced to federate with more successful schools - including grammars - or be converted into "trusts" run by governors appointed by private sponsors.

The very worst performers could be closed down and re-opened as National Challenge "super-trusts", run by a local grammar or successful comprehensive in partnership with a private company or university, Mr Balls said.

Sir Mike's panel will not itself have the power to go into schools and order headteachers to make changes.

It will, however, be able to advise Mr Balls on what actions the panel believes are necessary to rescue a school that is making no progress, and the minister will be able to force that institution to make the necessary changes. City academies, which are the direct responsibility of the Department for Children, Schools and Families as opposed to local authorities, will not be immune from that process, Sir Mike said. "As far as my group is concerned, we will be treating them exactly the same."

Mr Balls said the 638 schools fell into three categories.

A third were already "on the right track to success" and were expected to continue to improve. These schools are often graded good or even outstanding by Ofsted for raising the attainment of some of the most difficult pupils in mainstream education.

A third needed "intensive support" to improve poor standards of discipline, while the remainder needed a "more radical transformation", Mr Balls said.

This last group could conceivably include the Westminster Academy, which had one of the lowest proportions in London of pupils achieving five A* to Cs last year, at 17 per cent.

Twelve - or 18 per cent - of schools in London below the target achievement level are academies.

However, Mr Balls believes academies are already improving and a Schools Department spokesman made clear they would be left alone for as long as possible. "If they are on the right track, then we wouldn't intervene," he said.

Sir Mike, who was Ofsted chief inspector until 2002, said London had the lowest proportion of schools in the targeted group of any English region, at 11 per cent.

Four of the capital's boroughs - Camden, Hammersmith and Fulham, Kensington and Chelsea, Redbridge - had no schools where fewer than 30 per cent achieved five Cs or better last year.

In contrast Croydon had five, while Bexley, Greenwich and Haringey all had four.

Critics will say this is the latest in a string of failed attempts to reduce the long tail of under-achievement in state schools. Shadow education secretary Michael Gove said: "There are hundreds more where fewer than half the children get five good GCSEs and as a nation we are falling behind.

"The Government has no answer other then more bureaucracy and targets and they have no plans either to restore rigour to exams or freedom to professionals."