Schools in England are mostly satisfied with the way they are inspected by Ofsted, an independent report says.
Half of pupils did not notice improvement after an inspection
But it raises questions about how much the inspectorate helps schools improve.
Many told the National Foundation for Educational Research the inspectors merely confirmed what they knew already and were tackling, where necessary.
Ofsted says it has "work to do". Unions have questioned the millions of pounds it costs to run the organisation.
When 1,328 pupils were asked by pollsters Mori how much their school had changed, 9% said it had got much better - down from 12% three years ago.
Thirty per cent thought it was slightly better (down from 31%) and 45% thought it had stayed the same (41%).
'Work to do'
Asked what, if anything, the inspection had helped to improve, pupils highlighted the way the school was run and the quality of teaching.
Only 18% said pupils did better in tests, 12% thought their interest in learning was better and 9% noted an improvement in their enjoyment of learning.
Ofsted's director of inspection, Miriam Rosen, said there was "still work for us to do".
"We will continue to seek the views of parents, teachers and young people to ensure that we take their concerns into account."
She welcomed the way the vast majority of schools were satisfied with their inspections overall and found the process useful and helpful.
'Satisfactory' - not
The basis of the current inspection system is a lengthy self-evaluation form that school leaders must complete.
Ofsted then comes in to check their findings, rating schools as outstanding, good, satisfactory or inadequate.
"Satisfactory" is regarded as being not good enough.
The National Foundation for Educational Research (NfER) study was commissioned by Ofsted.
It involved a survey of 1,597 schools inspected between October 2005 and March 2006, with detailed visits to some.
Overall, it said, just over half (52%) were very satisfied with the inspection and just over a third (36%) rated it quite satisfactory.
More than two thirds agreed with Ofsted's recommendations to improve.
But NfER added: "More than half the case-study interviewees said the recommendations confirmed the areas already identified for action by the school."
A third thought some recommendations were too general, lacked practical advice, or failed to take school context into consideration.
Nearly two-thirds of survey respondents said the inspection had contributed to school improvement - but mainly by "confirming, prioritising and clarifying" things.
"More than half the head teachers and senior managers interviewed said that they had agreed completely or mainly with the recommendations, but about two-thirds of that group stated that all the issues were already being tackled."
Many parents could not remember the inspectors' report.
Some appreciated the fact that it was an independent assessment.
One parent said the report "was very detailed" but added: "You know, it actually told me exactly what I thought it was going to tell me."
The general secretary of the Association of Teachers and Lecturers, Dr Mary Bousted, said: "Can it really be justifiable to spend £200m of public money a year to tell schools something they already know?"
Self-evaluation was an improvement, making schools look hard at how they were performing, she said.
"But they can do this for themselves without the need for Ofsted to get involved."
The head of the Association of School and College Leaders, John Dunford, said: "This demonstrates that there is a case for fewer inspections and greater reliance placed on self review."
Ofsted's redefinition of satisfactory performance as unsatisfactory had been "both a distortion of the English language and a profoundly depressing judgement for many heads," he added.