It was an in-service day at Chiswick School in Hounslow, west London. Staff spent the day working in their departments on practical tasks arising from whole-school developments. The morning was spent looking at the grades that Year 9 pupils had achieved in the half-termly “portfolio” assessments for every subject.

They were trying to streamline all the data available on pupils, and maximise its usefulness for evaluating results and setting targets. The first task was to see if the percentages of students achieving different grades fitted the normal distribution curve. (“I’ve done a guide on how to calculate percentages”, Liz Allen, head of maths and a project leader, said helpfully).

If there was a skew to As and Bs, or Ds and Es, the assessments were probably too easy or too difficult. Indeed, the maths department found a big skew towards bottom grades and intended to rethink its assessment. Departments were also asked to compare the results of individual Year 9 pupils with information collected when they were 11 years old: verbal reasoning scores, reading ages, maths tests, information about Chiswick’s intake compared with national norms. A number of interesting points emerged about individual under-achievers, and problems with setting arrangements.

In the afternoon, departments finished what they called the Blue Peter project. Each department had been asked to produce posters for each year group to show to students and parents, demonstrating the difference between grades A , C and E. “Parents and some students often have no idea what a better piece of work would look like,” said Helen Metcalf, the headteacher.

The work was labelled with brief comments, showing why it had merited its grade. Staff said it wasn’t easy translating their partly intuitive sense of what makes a grade into lay language. Quite apart from its value for parents and students, it had been a useful professional exercise.

Ten years ago, on the evidence of a contemporary old-style HMI report, Chiswick would have been branded a failing school. Helen Metcalf came in as a new head with new deputies. Gradually the introduction of good, consistent management practices and a constant focus on the quality of teaching and learning have paid off. Results are now not only above the national average, but in the top 5 per cent of schools with a comparable intake, according to the latest national benchmark data.

Chiswick is an 11 to 18 comprehensive. About 30 per cent of its pupils get free meals. But it is now heavily over-subscribed, attracting middle-class, working-class and ethnic-minority families alike. As in all good London schools, it is easy to recruit excellent newly qualified teachers, but they move on (often for promotion) to areas where they can afford to live more comfortably. So turnover is high.

Advertisements for middle-management posts attract very small fields. Luckily, the opportunities for professional development that Chiswick offers mean it has groomed a lot of its own excellent middle managers. Clive Springham, second in charge of English, and a leader of the Blue Peter project, came to Chiswick as a newly qualified teacher six years ago.

“There’s a big emphasis on career development - always some new challenge,” he said. “There’s so much opportunity - I was joining policy teams in my first year here. You see how things work through, how initiatives inter-relate.”

More than one head of subject said that sorting out departments, sometimes from a low base, and building up resources, curriculum and teamwork, had been “down to me”. But they also said that the open doors and ready support of the senior team had been crucial. Money was found for them to modernise teaching resources or to provide training. “The structure of support in the school has been constantly improving,” said Giles Marshall, who had recently moved on from head of languages to acting head of sixth form.

Staff at all levels have helped to develop whole-school policies, for discipline, or assessment, recording and reporting.

From the start, Helen Metcalf constantly emphasised that unless lessons are interesting and challenging, you can’t expect students to behave, let alone learn.

“Year heads have moved a long way from rushing about with a blue light on their heads,” said David Brockie, a deputy head. “Now they manage cross-curriculum evaluation and the review of students’ progress.”

There is a strong emphasis on sharing good practice within and across curriculum areas. Recently a newly qualified teacher described ways of “framing” pieces of writing for less literate students to improve the quality of what they can produce, and the idea has now taken off in several departments.

Heads of departments have been encouraged to share responsibilities with their staff. Observing other teachers’ lessons is now routine practice.

Trevor John, the long-serving head of technology, has seen the school in bad days and good. “OFSTED in 1994 helped,” he said. “It made us focus on putting systems into place, and set a deadline for our good intentions. But what’s different really is that a climate of confidence builds up over time: people feel they can talk about problems, and suggest new ideas, and be supported. Teachers are now looking more to implications of changes for their whole curriculum area - not just their own classes, or subject.”

Terry Molloy, a deputy head who came from another school, said: “This school produces superb teachers, as well as managers. People who have left here, and moved on to other schools with less emphasis on the quality of teaching and learning, say they now realise that at Chiswick, they were at the cutting edge.”