It was not written in green ink, but it might well have been. It was certainly the most robust letter I received in my time as chief inspector of schools in England.

Signed “P Ireland, headmaster, Nelson Thomlinson school, Cumbria”, it set out the sins of two “arrogant, complacent and despicably unprofessional inspectors” who had recently visited his school. What, he asked, did I think I was doing, sitting comfortably in my office while my employees behaved “like lunatics on the loose”?

The school was a long way from my comfortable London office, but it seemed to me I had no option but to visit this hyperventilating head. It was one of the best professional decisions I ever made.

Within five minutes of my arrival, the ice had been broken and my errant inspectors forgotten. I was listening to a headmaster who cared passionately about his school and whose achievements were truly remarkable. Nelson Thomlinson became for me the bench-mark: if Peter Ireland could do it in pretty unpropitious circumstances why couldn’t every other head?

Last week, with Ireland’s retirement imminent, I returned. I was not surprised to find that the school had continued to progress. In 2006 around 70% of pupils achieved five or more A*-C grades at GCSE, not, as Ireland put it, “a bad achievement for an ‘average’ comprehensive school that does not make use of GNVQ scams, which equate to four higher grade GCSEs”.

That year, A-level results compared well with those of any other comprehensive school in the country. Five pupils went to Oxford or Cambridge. “The majority of pupils,” as a recent Office for Standards in Education report put it, “reach levels of achievement far higher than expected given their starting point and circumstances. This is an outstanding school.”

I must have met more head teachers over the years than pretty well anyone else in the country. Few describe themselves in interviews with their local papers as an “old geezer” who is “ridiculous”, “self-indulgent”, “chaotic” and “disorganised”. Most actually take themselves rather seriously. They like to go to meetings and pronounce. Ireland does not. He only went to one meeting last year, to see, he told me, what his director of education looked like. He prefers to be in his school, teaching and watching his teachers teach, leading from the front.

Year 7E, a class that does not find reading and writing that easy, clearly loved him. They fell over themselves in their eagerness to show me what they knew. “How,” he asked, “do you recognise a Norman church?” The hands shot up. “Rounded arch.” “Pillars like an elephant’s legs.” “A tympanum.” “Okay,” he replied, “who can spell tympanum?” The first two volunteers could not. Mock anger furrowed his brow. “What?” he bellowed. “You have just cost me my job. This visitor used to be in charge of all the schools in England. He’ll sack me immediately.” They turned to me imploringly. “Don’t, sir. He is the best teacher in the school. He makes lessons fun.” Discussing the lesson later, Ireland would have none of it. “There are plenty of teachers in this school who are far more skilled than I am,” he said. Perhaps, I thought, but they are going to have to be outstandingly good. What is clear is that this is a school which places teaching at the heart of its drive to raise standards. Where other schools follow the government’s lead and witter on about “learning”, driving their teachers to distraction with exhortations to plan lessons that connect with each pupil’s unique “learning style”, Nelson Thomlinson works from the commonsense assumption that the better a teacher teaches the more a pupil will learn.

Individual teachers are appraised regularly. Departments are inspected by the senior management team. Above all, every opportunity is taken to share high-quality professional expertise, both within departments and between departments. The most dramatic example of the latter is what I think is a world first: a professional development room. This is a full-sized classroom connected by two-way mirror glass to an observation room.

Teachers can demonstrate to their colleagues aspects of good teaching. Those watching discuss what they see with the help of a “coach”. Specific themes focused on recently included Teaching the Less Motivated, Effective Use of Group Work, and Managing Discussions.

Like most brilliant ideas, it could not be more simple. Seeing is believing. It is hard to think of a more potent tool for professional development. Are Nelson Thomlinson teachers threatened by all this observation? Far from it. One said to me that the support they were receiving was “the best thing professionally that had ever happened to her”. There was clearly an eagerness to volunteer to demonstrate lessons and an enthusiasm to hone skills.

When Ireland returned from two terms helping to rescue a failing school and put his own school into voluntary special measures there was a degree of shock, but equally a recognition that such an audit was “reasonable” and, interestingly, it fostered a competitive urge within the school to be the best department.

What staggers me is the lack of national recognition. Why hasn’t a government desperate to innovate and modernise and determined to fund every half-baked scheme dreamt up by an out-of-touch bureaucrat seized on the idea of a professional development room? Why hasn’t Ireland been dragged, kicking and screaming, to pontificate in Whitehall?

The answer is obvious. He left Nelson Thomlinson in 2000 to head up one of the government’s flagship academies. He lasted six weeks before he returned to the school. Why? Because he could not stomach the spin, the manipulation of the admissions, the arrogance and complacency of a governing body more interested in a national reputation than the reality of what needed to be done in its school. It is a parable for our times.

One question matters to Ireland and his staff: would it be good enough for my child? If every school asked itself the same question and ministers recognised that the only thing that matters is leadership, secondary education in England would be transformed.

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