Every time Carol Fitz-Gibbon steps out of her office at Durham University’s department of education she looks out to the great cathedral, one of the Romanesque wonders of Western civilisation, an ancient seat of learning and inquiry. But her own empire lies not within the university’s rambling medieval fabric. It is out on the city’s edge in the rapidly-expanding science park.

The Curriculum, Evaluation and Management Centre, that she founded and directs, is the largest provider of performance indicators for schools in the UK.

It has just moved to new premises, built for number-crunching and data evaluation, where Professor Fitz-Gibbon presides over a team of 17 research assistants, including mathematicians, computer scientists and physicists, handling a raft of performance information systems for schools.

She has been the pioneer and is the queen of value-added in this country, providing thousands of schools with externally measurable indicators of the value they add to pupils’ attainment.

In addition to raw exam results, she looks at student satisfaction and related issues such as class size, time allocated and teaching strategies on the basis of a year-by-year, pupil-by-pupil, subject-by-subject scrutiny.

Professor Fitz-Gibbon believes her work has taken off because she provides schools with the evidence they need to produce clear and informed strategies. As a former maths and physics teacher she has seen it as her quest to “do good science” in education. She objects fundamentally to judgments being made without sound evidence.

After studying at London University, she began her career teaching physics in a Cheshire grammar school and moved on to inner-city secondaries in Hackney, where she worked part-time while she raised her two children.

Fourteen years in the United States followed because of her husband’s job, where she spent two teaching at an affluent private school and four teaching street-wise, disadvantaged children in inner-city Los Angeles.

During this time in LA, she became interested in cross-age tutoring, motivating disaffected older children by involving them in teaching younger children. This grew into a central research interest which she continues today.

During an MA undertaken at the University of California Los Angeles into the identification of inner-city, clever students, she became deeply interested in evaluation and research methods.

The fact that in both the UK and US she taught across the social spectrum sowed the seeds for her interest in value-added.

She became passionately concerned to provide concrete evidence of the real difference that teachers can make to children all across the ability and social range.

Some of her peers believe she takes this to extremes; that she has a narrow view of what counts as good evidence; that it is not possible always to measure things in the way she would want; that evidence can be more broadly based; that her combative nature and ready criticisms are not always helpful. But few doubt the fundamental importance of her critique.

It is this which has brought her into conflict with the Office for Standards in Education and into a seemingly permanent state of locked horns with Chris Woodhead, its chief inspector. Since OFSTED’s inception she has been snapping at its heels, berating it for making judgments she believes are based on insufficient or flawed evidence.

She also objects to OFSTED’s system of benchmarking, which ranks schools according to “postcode analysis”. She believes no two schools are alike and benchmarking and ranking of whole schools is too crude. “There are no similar schools, only similar pupils. You can only measure pupil intake and progress. OFSTED is wedded to inaccuracies; it is amateurish,” she says.

Mr Woodhead, for his part, has written that Professor Fitz-Gibbon has a fundamental objection to exposing schools to public scrutiny.

The chief inspector is, she claims, a blessing in disguise: “If we had a more temperate and cautious person it would have taken us longer to see that the methods were wrong. My fear is that if he goes the methods will stay.”

So incensed is she by the methods and the unnecessary pain she believes OFSTED has inflicted on teachers, that she has instigated OFSTIN (the Office for Standards in Inspection) now run by a group of retired headteachers and a recognised pressure group. It gave evidence, for example, to the MPs currently looking into OFSTED’s work.

The best inspection system, she believes, consists of light monitoring based on validated self-evaluation and informed by value-added systems. One or two inspectors should drop into schools unannounced and make their judgments based on what they see and “the information the school has of itself”.

On the positive role of value-added she is little short of messianic. She says: “Value-added will stay when benchmarking, target setting and performance-related pay have gone. They will go because industry left them behind years ago and went into human resources management because that’s about quality of life and the recognition of commitment.”

Professor Fitz-Gibbon, it seems, is also here to stay, despite the fact that retirement looms “all too soon”. She said: “I don’t want to retire and I won’t leave easily. I’m determined to carry on.”