The increasingly detailed nature of test data in Britain has prompted concerns that teachers may be scored according to pupils’ results.

One teachers’ union has found that a handful of schools are going against legislation and using test results as the main way to evaluate their staff’s performance.

But in New York it is starting to happen on a large scale, with official backing. The city has announced an experiment in which 2,500 teachers in 140 schools will be rated individually, based on how much their pupils’ results improve.

Officials have said it is too early to confirm how the information will be used, but it could determine their pay and performance evaluations. The ratings may even be made public, so pupils, parents and fellow staff members can see them.

The development, which has angered teachers in New York, comes at a time when teachers in Britain face unprecedented scrutiny of their pupils’ results.

The exam board Edexcel last year introduced Results Plus, a data analysis system that lets schools - and potentially pupils and parents - see how a teacher’s pupils have fared on individual questions in an exam.

Jerry Jarvis, managing director of Edexcel, was recently quizzed about the system’s potential when he appeared before the Commons education select committee.

Graham Stuart, Conservative MP for Beverley and Holderness in East Yorkshire, asked: “Will we move to a stage where politicians are saying to every teacher below a certain level, ‘You are going to be sacked in one or two years’?”

Mr Jarvis denied this would occur. “Right now, teachers are vulnerable to being sacked for their exam performance as defined within league tables,” he said. “Results Plus will prevent that happening by helping to improve their performance.”

Chris Keates, general secretary of the NASUWT, said the union was already challenging a few schools which were trying to base performance evaluation on crude data. Some relied on pupil test scores, others used scores from lesson evaluations or combinations of the two.

“Such simplistic number-crunching appeals to some schools because of our test-driven system,” she said.

But she was confident this would be stopped because the revised performance management arrangements for teachers clearly stated they should not be judged on such crude factors. She also hoped those regulations would act as a safeguard if British politicians tried to copy the New York system.

Some New York schools participating in the rating trial have not told their teachers. A two-page report will be produced on each teacher, showing how their pupils have performed against predicted results. They can also be compared against colleagues across the city.

Chris Cert, the deputy schools chancellor for New York, said that making such information available to the public would be “a powerful step forward”.

But the United Federation of Teachers, the city’s teaching union, said it would oppose attempts to use the data to evaluate its members’ work.

A union spokesman told The TES that one flaw with the approach was that it relied on comparing pupils’ scores from tests in January with their scores in January the previous year. However, like in the UK, their school year starts in September, so pupils would have had two teachers during that period.

“The tests were never designed to evaluate individual teachers,” he said. “Judging any teacher with student test scores is fundamentally flawed.”

In 2005, Ruth Kelly, then education secretary, told The TES she would not condemn heads for using pupil-level test data to dismiss staff.

A spokeswoman at the Department for Children, Schools and Families said that there were no plans to introduce a system that measured individual teachers by their pupils’ results in England.

‘THERE’S A SPIRIT OF THE KGB ABOUT IT’

The end could be in sight for the “rubber rooms” where New York teachers can be sent to sit, sometimes for months, if they have been accused of misbehaviour.

The city has 12 “temporary reassignment centres”, where suspended teachers must sign into from 8am to 3pm to remain on full pay as they wait for their disciplinary case to be settled.

Often a teacher will not even know why their school has made them register at a centre, nicknamed a “rubber room” after the slang for a padded cell.

The reasons for suspension range from the trivial - say, talking back to a headteacher - to serious charges such as assaulting a pupil.

One teacher, sent on unspecified charges, told The New York Times last year that the windowless Manhattan centre was designed for about 26 people but often held more than 75. “There is a spirit of the KGB about it,” he said. “There’s friendship and camaraderie among us in the room, but there’s also a constant atmosphere of fear.”

But the education professionals’ version of Guantanamo Bay detention centre may face closure. Last week a group of teachers filed a legal suit, describing it as a “modern-day internment camp”.