When the Office for Standards in Education inspectors arrived at St Mary Magdalen’s primary school in Accrington last October, they were greeted with a level of optimism and enthusiasm they must rarely encounter.

“I thought we would do so well,” said the Lancashire school’s headteacher Justine Chadwick, “because we’ve achieved so many things. The school has such a huge vibrancy about it. There’s a real buzz in the building.”

No one denied the Church of England school had problems. Many of its pupils came from a ward with the fourth highest level of deprivation in the country, and Mrs Chadwick was determined the school should remain inclusive, often taking children excluded from other schools. Ofsted’s previous report rated the school’s work satisfactory, and the local authority believed it had made good progress since then.

So there was a sense of shock when, on the first day of this new inspection, a lesson was found to be unsatisfactory. The following day, two more were marked down - one because, although children were paying attention, they “looked bored”.

Mrs Chadwick was incredulous. “When my children are bored they go upstairs and flood the toilets or set off the fire alarms,” she said. “That’s more the style we’re used to.”

On the third day, HMI arrived to monitor the inspection, one of the first to take place under a new Ofsted framework introduced last September. No more lessons were failed, but at the end of the visit Mrs Chadwick was told the school had serious weaknesses. She believes that if it had been inspected a term earlier, under the old framework, this would not have happened.

“I think our desire to be totally transparent worked against us because the framework didn’t allow the inspectors to be flexible,” she said. “My strong feeling was the report was written before they ever arrived in school.”

The new framework was meant to make life easier for schools. It was billed as “light-touch” inspection, with shorter visits to schools and a much greater emphasis on self-evaluation. But many schools, including St Mary Magdalen’s, now feel something has gone strangely awry.

Last term, David Bell, the chief inspector, confirmed suspicions that there had been a rise in the number of schools found to be failing. In the first half-term of the new regime, he told the Commons’ education and skills select committee, 46 schools were placed in special measures and 39 were found to have serious weaknesses - respective rises of 35 and 30 per cent over the same period the previous year.

The issue of failing schools will form a major plank in Mr Bell’s annual report next month. So what is happening in schools, and is the new framework to blame? Almost everyone in the inspection world who is prepared to talk about the issue at all - and many are not - believes the framework is at fault.

Liz Walker, a former head, National Association of Head Teachers’ secretary for Sandwell and current Ofsted inspector, spells out graphically how the new inspection criteria have forced her to change her judgments on schools.

“On the training day with HMI we were shown video clips of a lesson and asked to grade it,” she said. “In the past, I would have given that lesson a grade four on the seven-point scale, which is satisfactory.

But with the new criteria in front of me I could see it had to be a grade five, which is unsatisfactory, because the lesson’s objectives weren’t met and because the children didn’t make progress.

“I felt very unhappy at giving that lesson a five. And what really opened my eyes was that, within the group I was working in, there were grades given ranging from two to five.”

Her experience, like that of St Mary Magdalen’s, goes to what many people feel is the crux of the matter. What used to be satisfactory, in Ofsted terms, no longer is. As Mr Bell and his colleagues explained to the select committee, a single satisfactory lesson is still considered satisfactory, but if lessons across the school are only satisfactory and rarely better, then the school is failing its pupils. This, many observers say, has led to a ratcheting up of standards.

Shorter inspections and the greater emphasis on self-evaluation have emphasised the effect, according to Graham Jones, the co-ordinator of Exeter university’s school improvement unit and a former registered inspector. Schools now have to show the inspectors their strengths and weaknesses instead of waiting for them to find them: “Where it used to be a game of hide and seek, now it’s show and tell,” he said.

What many headteachers do not realise is that if they mark themselves high so that inspectors will have to argue them down, rather than up, they may actually be marked down for poor leadership and management, he says.

Furthermore, under the old, longer inspection, there was time for teachers to settle down after first-day nerves, but now the process is condensed and those early, often poor lessons can form a key part of the inspectors’

judgments. This is particularly pronounced in smaller primary schools, where one lesson can now produce a significant proportion of the marks for the whole inspection.

So far, so simple. But within the walls of Ofsted’s headquarters, officials are wrestling with a much deeper puzzle in advance of next month’s annual report. New figures to be contained in the report, and released to the TES, show the rise in failing schools actually pre-dated the new inspection regime.

The number of schools placed in special measures rose last year for the first time in several years. After falling from a high of 290 in 19978 to a low of 129 in 2001-2, the figure leapt up to 160 last year. That pushed up the proportion of failing schools among the total inspected from 2.8 per cent in 20001 to 3.5 per cent in 2002-3. In the first half-term of this academic year there was a further leap, to 4.5 per cent of all standard Section 10 inspections.

Ofsted has refused to comment at this stage on what it thinks is going on - it is too early to give full reasons for this apparent outbreak of failure, it says. (David Bell is also about to announce changes which will put even more emphasis on self-evaluation and involve even shorter inspections.) In his session with the select committee, Mr Bell said he thought part of the reason could be a surge in the number of re-inspections of schools previously found to have serious weaknesses. It seems that once a school has serious weaknesses, escape is difficult - except into special measures.

Others believe the new inspection framework has accelerated a process which was taking place anyway. Brian Oppenheim, director of inspections with the Inspection and Consultancy Partnership, which is carrying out 80 Ofsted inspections this year, feels the process has become progressively sharper and more targeted.

“A lot of the schools coming up for inspection were last visited six years ago, in 1998. Everybody has moved on a bit since then, and inspectors have had to become sharper and more focused. I suspect it isn’t going to go away. The bottom line for us is: are the kids getting a good enough deal? That really is the driving force behind this framework.”

His words will bring little comfort to Justine Chadwick and her staff at St Mary Magdalen’s.

“I can’t believe I could ever have been so optimistic,” she says. “I think the really serious weakness in this school was my naivety.”