Most of the schools that have been identified take children from difficult or poor backgrounds - with the exception of two or three primaries set in relatively affluent rural villages - though there may well be thriving schools with similar intakes.

What appears to set this group of failing schools apart - and the count is expected to rise to between 250 and 500 by the time the inspectors have visited all schools - is the low standard of achievement by pupils. The reports regularly cite poor teaching as a factor, and there is a significant number where the disruptive behaviour of pupils is a serious problem. There is even an infants school, Mayville in the London borough of Waltham Forest, where inspectors found regular disruptive behaviour.

One of the Hackney primaries, Morningside, is described as having low standards of behaviour that contribute to the school being neither safe nor secure. The same school has a significant number of teachers who lack the knowledge and expertise required for some of their subjects.

However, the secondaries are a more homogenous group than the primaries. All but one are in urban areas; most have large numbers of black or Asian pupils and inspectors often comment that teachers have low expectations of their pupils.

Among the primaries, inspectors have tended to point more to weak heads and ineffective management often combined with unsatisfactory teaching. The 71 pupils at Urchfont Church of England School in Wiltshire come from relatively affluent backgrounds, but the inspection report points to major weaknesses in the head and management team. The other factor common to several schools is the inability to teach children adequately at the upper end of the school, an issue that the Office for Standards in Education has raised elsewhere.

It is relatively early for any useful research on whether there are common factors - only 3,000 of the country’s 26,000 schools have so far been inspected - and it will be another three years before the job is complete.

For whatever reason, the 51 identified so far were found to be in a bad way (another 10 are in the pipeline) and debate rages over what needs to be done. Michael Barber, professor of education at Keele University, is suggesting that the very worst - maybe a handful - should be closed and a new school opened on the same site. The school would take back the same pupils, but there would be a new team of teachers. He also makes a case for school inspection teams to be given powers to report confidentially to heads on poor teachers and such reports used to trigger competency proceedings.

In support of such radical measures, he cites the work of David Reynolds at Newcastle University that suggests failing schools may not just lack the qualities of an effective school but may have characteristics that militate against efforts to turn them round. Staff relations may be a mess in such schools; the culture may be one of blaming children for poor standards with even effective staff hiding behind the norms of the ineffective group.

Professor Reynolds himself believes that schools in this category cannot be left to improve themselves and outside intervention is required, though he is not convinced that it is necessary to close the worst. While he accepts that quality of teaching has to be tackled, he also thinks it would be unjust to sack individual teachers before trying to improve their skills.

Within OFSTED, there is a view that most local authorities have acted decisively in dealing with failing schools. A number of heads have been retired early and, in the case of Hackney Downs, the council has decided to close the school. There are also three other secondary schools which would probably have closed anyway.

There remains the problem of dealing with failing grant-maintained schools - of which there are currently only five - but they have neither budgets nor an obvious source of outside expertise upon which to call.

The fate of failing schools is decided by the Education Secretary advised by officials in the Department for Education’s school effectiveness unit. The DFE expects to see significant improvement after 12 months and schools have another 12 months in which to demonstrate they are no longer failing.

No school has yet had its allotted two years, but the Education Secretary may have to consider whether she should send a “hit squad” or education association into a couple of schools by the turn of the year.

Peter Mortimore, director of the Institute of Education at London University, which has set up the International School Effectiveness and School Improvement Centre, points out that academics have traditionally believed that it takes between five and six years to turn a school round.

However, he acknowledges that the OFSTED process has served to concentrate minds and hard decisions have been taken about replacing heads and teachers. He has doubts about whether the Barber strategy of closing down the worst schools actually solves the problem. The difficult pupils remain to be dealt with and the entire staff - including good teachers - are likely to feel resentful, he says.

Schools fail, he says, for a mix of reasons. Some start off with the inherent disadvantages of being located in areas of high unemployment where it is harder to motivate and inspire. In others there is poor management and heads and staff do not work as a team. Some schools, he says, are just unlucky and have heads who cannot cope.

The search for solutions has meant ministers and DFE officials taking trips to the United States where the school improvement movement is far more developed. For now, local authorities have mainly opted for changing the senior management of such schools and sending in teams of experienced teachers to work with existing staff. Only one or two have not shown any significant improvement.

It would take some courage o send in an education association to a school that had resisted the best efforts of a local authority. It is unclear what team of experts the DFE could put together and just what they might be able to do.