The role of the chief inspector of schools is "out of control" and the post should be brought back under the authority of the Education Secretary, according to a previous chief inspector.
In a damaging critique Eric Bolton, who held the post of senior chief inspector between 1983 and 1991, accuses Chris Woodhead of mixing up evidence with personal polemic and using unprovable statistics to justify his pronouncements.
Professor Bolton also accuses the Office for Standards in Education of being "out of touch" and incapable of reliable advice or insight.
The attack is all the more remarkable as Professor Bolton has previously shunned publicity. His criticisms, he insists, are aimed more at the structure of OFSTED than Mr Woodhead himself.
Writing in the Oxford Review of Education he argues that OFSTED and the chief inspector should be brought back under the control of the Department for Education and Employment.
Unlike the old HM Inspectorate, OFSTED was removed from DFEE control when it was set up in 1992. Mr Woodhead's role is to advise the department, but he is accountable to the Prime Minister.
"The independence conferred on the HMCI has created a post that is out of control," says Professor Bolton. "The HMCI can range where he will and justify his pronouncements by selecting as he pleases from the huge mass of inspection data that now exists.
"No one and no agency is in a position to gainsay him, largely because there no longer exists a standing body of expertise within the inspection arrangements that could state with reasonable certainty and credibility what the inspection data reveal and the range of legitimate interpretations."
Professor Bolton also accuses Mr Woodhead of mixing personal opinion and OFSTED judgment.
"The HMCI has openly chosen to be polemical and to express his own views on important matters," he writes. "The problem is that it is not clear when the HMCI is expressing his own opinions and when he is voicing a collective judgement."
He adds: "OFSTED has had to develop a highly prescriptive, dirigiste framework for inspection. It is too inflexible to allow individual schools' strengths and characteristics to emerge."
And he says OFSTED fails to take into account the first signs of serious problems ahead. "Inspection teams could soon be describing no more than the wallpaper of an out-of-touch inspection framework."
Eric Bolton, who was professor of teacher education at the Institute of Education in London until recently, calls for:
* a larger inspectorate brought back within the "locus" of the Education Secretary;
* a remit to advise policy-makers;
* a more cohesive inspection force with a sense of collective experience and expertise.
Speaking this week he said: "There are things which seem to me quite exasperating. Nobody has any real idea what OFSTED's evidence adds up to."
Before OFSTED, he said, the chief inspector's evidence was a trusted part of government policy-making. He in turn was held accountable by other inspectors. "Michael Barber's whole (Government) standards and effectiveness unit is a substitute for what HMI used to provide," he says.
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