Heads are resigning after their schools were failed by inspectors following poor Contextual Value Added ratings.
Two headteachers of otherwise successful schools have spoken to The TES after receiving damning inspection judgements driven, they say, largely by CVA.
Charlie Lupton, head of St Barnabas Church of England first and middle in Drakes Broughton, Worcestershire, is thought to be the first to stand down.
The school was placed in special measures following a visit in January.
Yet the school - which unusually takes 4 to 12-year-olds - attracts children from well outside its catchment area. It has received Artsmark and Activemark gold awards, and in February was found by C of E inspectors to be a "good church school" led by a head of "vision and tenacity".
However, it appears to have paid the price for a set of poor key stage 2 results. In 2005, these were just below the national average, despite the school serving a relatively prosperous area.
Mr Lupton told The TES that inspectors, who rely more on data in new inspections lasting less than two days, no longer had time to understand the school. He said: "There are a lot of subtleties to get your head around in just two days, and none of the inspectors had visited a similar school before."
A teacher at the school wrote to the inspectorate to complain that its judgement did not mention the hard work of staff. Ofsted replied that its reports "analyse outcomes for children within the school".
Another head, who asked not to be named, resigned after her Midlands primary was placed in special measures despite featuring in The TES as a centre of creativity, and being praised by its local authority. The head said "(the inspectors) were not interested in anything that wasn't measurable by Sats. They had a very shallow understanding of what we were trying to do".
Chris Conway, assistant head of Archbishop Grimshaw, in Solihull, which failed an inspection three months ago, said its CVA would be transformed if it excluded 15 badly behaved pupils in each year. But it had refused to do so and chose to stand by the children.
He said heads should be getting knighthoods for working in challenging schools, "not finishing their careers with this cloud hanging over them".
An Ofsted spokeswoman said: "Ofsted has emphasised to both HMI and additional inspectors that performance data and indicators, including those for CVA, inform, but do not determine, inspection judgements.
"Judgements should be made by inspection teams on the basis of all the evidence available, including first-hand evidence gathered during the inspection."
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