By Gary Eason
Education editor, BBC News Website
The head of Ofsted has asked teachers to tell her about the over-zealous use of performance data by inspectors.
Chief inspector of schools Christine Gilbert said she had already received "numerous complaints" about new data designed to show children's progress.
Ofsted is 'thinking hard' about ways of improving performance measures
She stressed that the data should inform judgements about England's schools, not dictate them.
"Write to me if you have concerns," she told a teachers' union conference in Birmingham.
Ofsted was ''continuing to think hard'' about the new performance measure and ways of improving it, she said.
Contextual value added (CVA) data seeks to show the progress children have made from one stage of schooling to another.
It takes into account factors which are known to have an impact on this but which are beyond a school's control, such as ethnicity and poverty.
Armed with data
Schools' results were published in the annual secondary league tables for last year and will be in this year's primary tables.
Ofsted inspectors are said to arrive armed with the data and, some schools have said, appear already to have made up their minds in advance of a visit.
''No single indicator can tell the whole story about a school's work,'' Ms Gilbert told the NASUWT conference on public accountability.
She also said that, to her surprise, teachers had been complaining to her that under the new shorter inspection arrangements their lessons were not being observed.
Earlier at the conference the NASUWT's general secretary, Chris Keates, called for Ofsted to be scrapped.