Head teachers have challenged the findings of an Ofsted report saying school staff welcome its inspections.
Ofsted said it was "well-regarded" by most head teachers
The English education watchdog said a survey responded to by 2,801 heads had shown Ofsted's activities were "well regarded" by 90% of schools.
It added it had been "highly effective" in drawing the public's attention to education issues in the past 12 years.
The Secondary Heads Association said many teachers still found inspections "intimidating and stressful".
The report - Improvement through Inspection - found the most effective schools thought of inspections as "free consultancy".
The least effective followed the recommendations in order to improve, it said.
The report added that one million children had benefited from the improvements made to schools identified as requiring special measures - those given a deadline to improve or face closure.
Ofsted's figures also showed that four times as many head teachers found inspections of benefit to the school as found them detrimental.
However, Ofsted did find there was still "significant apprehension about inspections".
England's chief inspector of schools, David Bell, said: "I'm pleased that the findings from today's report are so positive. Our aim is to improve the quality of education throughout England, and these results show much progress has been made in achieving this."
Martin Ward, deputy general secretary of the Secondary Heads Association, said: "It is ironic that the work of schools, most of which are very well regarded by the children and parents who use them, requires an independent body for scrutiny, while the work of Ofsted can be evaluated by itself.
"SHA does not believe that the evidence for the good value of the Ofsted process is at all secure. In particular the 'special measures' labelling of schools, mostly those working in the most challenging circumstances, continues to do great damage."
Mr Ward added: "The improvements made in these schools (as in others) are made by the efforts of those who work in them, not by visiting inspectors.
"The Ofsted inspection process is unscientific, it relies too heavily on poorly chosen statistical performance indicators, and the quality assurance intended to ensure consistency of judgements is internal, as are the processes for complaints and appeal.
"Many teachers and school leaders continue to find Ofsted inspections intimidating, time-consuming, stressful, and distracting from their proper work of education."
However, the union said Ofsted had improved and that more inspections were now "sound and satisfactory experiences".
At present, inspectors give schools six to 10 weeks' notice before a visit, which happens on average every six years.
Most head teachers who responded to an Ofsted consultation earlier this year supported shorter notice and shorter, more frequent inspections.
The heads' association said a proposed new framework, based on these findings, would be a "further step in the right direction".
Chris Keates, acting general secretary of the National Association of
Schoolmasters Union of Women Teachers, said: "Schools which have had the
findings of their self-evaluation reports analysed, scrutinised and criticised
by Ofsted may feel somewhat aggrieved by Ofsted's benign, self-satisfied and
rather smug approach to the outcome of its own self-evaluation."