Ken Muller sits in his NUT office, on the disused top floor of a primary school in the London borough of Islington. Reached by flight after flight of discouraging stone steps, the room could be a metaphor for where some in New Labour might like to see all trade unions: inaccessible and out of sight. Mr Muller, whose face flushes with emotion when he talks about his school, has a handshake more like a shotputter’s than a history teacher’s.

It is a sign of the strength and tenacity that led him earlier this year to shed light on one of the murkier chapters of Islington Green’s contested history.

The story of Islington Green comprehensive is a story of high politics and how it impacts on the least powerful, on inner-city children, who have no votes or choices. Eight years ago, many people believe, those children were done a grave and lasting injustice. Now, as the country goes to the polls once again, a new battle is being waged with uncertain outcomes for the vulnerable young people this school serves.

On the morning of May 2 1997, Ken Muller arrived at Islington Green with a bottle of champagne. Ofsted inspectors had left the school the previous day; the Tory government had been buried in a Labour landslide; Tony Blair, an Islington resident, was moving into Downing Street; half-term was the following week. Life was sweet.

But the celebrations after school were short-lived. When headteacher Tony Garwood called staff together to tell them they had failed the inspection, there were cries of disbelief. Teachers knew the school had problems, but were convinced it was not failing.

Ken Riddell’s design and technology department had been described as a centre of excellence in the previous inspection report, and had improved since. It was just one of a number of robust departments, with a mix of experience and new enthusiasm, drawing in not only local families but parents from neighbouring Hackney. Morale was good, GCSE results were respectable: 38 per cent were getting five A*-Cs. The judgment made no sense to him. “We didn’t believe it, because we knew it wasn’t true,” says Ken Riddell. “We thought it was a mistake that would be sorted out.”

Islington Green - the green is a triangle of municipal grass some distance away -serves the Packington estate and surrounding social housing. The school building is distinguished by its folly - a 1960s seven-storey tower block, serviced by unusable 40-person lifts. In the mid-1990s, the school had a popular and progressive headteacher - Christine Peters, now at Parliament Hill girls’ school in Camden - and a confident body of staff.

The few middle-class children helped in the mix. “Their ability and social skills had an impact beyond their number,” says John Challinor, then deputy head. Euan Blair, famously, could have been one of them, but Tony and Cherie passed over Islington Green in what was seen by many as the first major betrayal of principles by the then leader of the opposition.

Peter Hyman - at the time a speechwriter for Tony Blair, now a classroom assistant and senior manager at Islington Green - recounts in his book, One out of Ten: from Downing Street Vision to School Reality, the mood in the Labour camp when the news broke in 1994 that Euan was to attend the grant-maintained, selective, Catholic London Oratory school. “I remember our panic... we wanted nothing to stand in the way of election victory.”

By 1997, Islington Green had a new head - Tony Garwood - and the school was becoming a victim of its own success. With the second-best GCSE results in the borough, more local parents were using it, and the professionals from beyond the catchment area were being squeezed out. The intake was changing and the school was not responding fast enough. Some staff felt they went into the Ofsted inspection insufficiently prepared and that was why they failed. When a team of HMIs arrived in early June to corroborate the Ofsted judgment, staff pulled together to show the school at its best. The visit appeared to go well; when they heard that they had been confirmed as failing, staff and parents were devastated.

“The school imploded,” says Con McCartney, then leader of the well-regarded English department. She resigned when the headteacher, under enormous pressure to make visible changes, discarded mixed-ability teaching. “We felt professionally very kicked, first by Ofsted then by the head.” By the start of the following year, five members of the English department, including both post-holders, had left. Within two years, almost all the teachers present in 1997 had gone. Con McCartney, now a teaching mentor in Hillingdon, has not taught since. Ken Riddell left to fit kitchens. Former head Tony Garwood moved “out of the frying pan into the fire”, he says, taking on East Brighton College of Media Arts. He now teaches in an international school in Spain. Ken Muller, now head of history, is one of the few to have stayed.

Even children who did well were left with tainted memories. “The effect on the kids was appalling,” says Rachel Burns, then deputy head of English.

“They went to a rubbish school, they were rubbish. Some of them thought it was their fault.” Many children left immediately, pulled out by worried parents. GCSE results dipped below 25 per cent and the school went through nine inspections before it finally came out of special measures in 2000 and serious weaknesses in 2003.

While school managers had from the outset urged staff to accept the decision and not be “in denial”, some never did. Ken Muller, the school’s NUT rep, continued to maintain that an injustice had been done. He and others believed that the school had been failed for political reasons: to justify the Blairs’ decision to boycott it and to show that New Labour, with its policy of “naming and shaming” failing schools, would be as tough on school standards as its Tory predecessors. Some also believed the failure was part of a softening-up of local education authorities to pave the way for privatisation (Islington was the first borough to be handed over to private contractors, when Cambridge Education Associates took control in April 2000) and to show the teacher unions -particularly strong in the borough - who was really in charge.

Fast forward, to last Christmas holidays. On the first day of the new year, Ken Muller made an online request to Ofsted, under the new Freedom of Information Act, to see the documents relating to the judgment. Twenty working days later, he got a reply. Most of the documents had been destroyed, said the email, but there was one that might be of interest.

Attached was a memo dated November 1997, from HMI Barry Jones to the then chief inspector Chris Woodhead, making clear that the HMI team, of which Jones was a member, had disagreed with Ofsted’s judgment, and noting that they were “of the unanimous view that the school was not failing”. “I could not believe what I was seeing,” says Ken Muller. “I sat there for five minutes, looking at it. I felt a tremendous sense of vindication, not just for me but for everyone.”

Barry Jones had asked the chief inspector the question teachers wanted answered. Why was the school put into special measures? A handwritten note from Chris Woodhead at the top of the memo says that Liz Passmore, then Ofsted’s head of school improvement, would explain the decision to Mr Jones when she saw him. Barry Jones, now semi-retired, has not come forward to offer further information.

Since then, Ken Muller, outgoing local Labour MP Chris Smith and former head Tony Garwood have all written to Education Secretary Ruth Kelly and to the current chief inspector, David Bell, demanding an apology and a retrospective overturning of the decision. Neither has been forthcoming.

Ruth Kelly has replied saying that Ofsted is independent of government; David Bell has said he has reviewed the evidence (despite Ofsted’s claim that all the other evidence has been destroyed) and that the decision was “properly made”.

Chris Woodhead is not pleased to be asked about events at Islington Green in 1997. “Why are you doing this?” he barks. He denies categorically that there was any pressure from ministers in the new Labour government to fail the school, saying there was no discussion and “there are absolutely no grounds for allegations of this kind”. Mr Woodhead says he made the decision after discussions with Liz Passmore. “She thought they (the HMIs) had got it wrong,” he says. He agrees that when the chief inspector overturns the recommendation of his own HMIs (as David Bell did five times last year) the process ought to be in the public domain. “I am all for transparency. There is nothing I did that I would want to hide. We did what the legislation required us to do. Decisions of HMCI were meant to be confidential, to do less damage to the school.”

Liz Passmore, now retired from Ofsted and involved with the Gems chain of private schools, says she met with Chris Woodhead and Mike Tomlinson, then Ofsted’s director of inspection now also working for Gems, and discussed the findings from the two visits. “After considering all the evidence, HMCI came to his decision,” she says.

But as another general election looms, former teachers and pupils have the satisfaction of what they believe is a moral victory. After the uncovering of the memo, 30 former teachers met in a pub close to the school one February night, coming from as far afield as Devon and Leicester, and tried to set to rest the sense of injustice that has lingered for almost a decade. Ken Muller received a standing ovation at the NUT’s Easter conference when he said Chris Woodhead should be named and shamed along with the then education secretary, David Blunkett, and Tony Blair.

Now, a new drama is being played out at Islington Green, once again reflecting wider political issues. A feasibility study is underway to turn the school into a city academy, along with Moreland primary school. Richard Cloudsley special school would share the proposed new site. Islington Green is under the leadership of Trevor Averre-Beeson, who works closely with Peter Hyman. The potential sponsors of the academy are a group of financiers in London and New York who have formed an educational charity called Ark (Absolute Return for Kids). Set up four years ago, it intends to sponsor seven academies in London and is at the feasibility stage for the Islington academy and another in Southwark.

Once again, the opinions of teachers and parents may not count for much.

Ark is keen to consult with the schools and wider community, and genuinely wants their support. But there is no mechanism for a ballot and the Department for Education and Skills makes the final decision on whether to proceed. “The whole picture is taken into account in coming to a decision,” said a spokesperson, in words that will probably fail to reassure many.

Headteacher Trevor Averre-Beeson describes the proposals as a “fantastic opportunity for investment not only in buildings but in restructuring the way in which the school is going to function”. He believes strongly that the “schools within schools” model championed by Ark will benefit children at Islington Green. Nevertheless, the news on academies has been almost unremittingly bad, whether it has come from the select committee, departing academy heads or exam league tables.

As a union activist and member of the Socialist Workers party, Ken Muller is at the centre of a campaign in Islington to halt the proposed academy.

“Ark promises to offer ‘a wealth of experience’,” he says. “But what they have is ‘an experience of wealth’. In terms of the values they represent, greed is good. What have these business people got to offer, to help us run a school?”