Being judged as failing by Ofsted can drive underperforming schools to make "significant and sizeable" improvements to their results, research has concluded.
The "public shame" that comes with a poor judgement is a "major spur" for schools, academics have found.
Dr Rebecca Allen from the University of London's Institute of Education (IoE) and the University of Bristol's Professor Simon Burgess also backed plans from Ofsted's new chief to intervene in more schools. "Sir Michael Wilshaw has argued that schools just above the fail grade should also be tackled; that 'satisfactory' performance is in fact unsatisfactory," they said.
"Such interventions in 'coasting' or 'just OK' schools are very likely to be of the same form as notice to improve. Our results suggest that this is potentially a fruitful development with some hope of significant returns."
The researchers compared the performance of secondaries that "just" failed their Ofsted inspections and were give a "notice to improve" to those that "just" passed and were given an overall "satisfactory" rating but failed on some criteria.
After stripping out other possible reasons for different GCSE results, such as changes in pupil background, they concluded that failing an inspection had "a big effect". On average, it meant a one-grade improvement for each individual pupil in "one or two GCSEs". For schools, it meant an average 5 percentage point improvement in the proportion of pupils gaining five or more A*-C GCSEs.
The researchers said their evidence suggested that the turnaround was lasting and came from "proper improvements in teaching and learning, not gaming to boost exam performance through switching to easier courses". They added: "The instruction to the school to improve its performance may empower headteachers and governors to take a tougher and more proactive line about school and teacher performance.
"The school management learning that what they might have considered satisfactory performance is unacceptable may have a major effect. The second part of the treatment derives from the fact that the judgment is a public statement and so provides a degree of public shame for the school leadership."
Brian Lightman, general secretary of the Association of School and College Leaders, said: "There is no question that if Ofsted outlines points for improvement then schools will address them. So I am not surprised at these findings.
"But I do not think this report should be used as a justification for an increase in the number of schools that are put into categories," he added. "It is a particular tool for schools in significant difficulties and if it starts getting watered down there is a risk it could be less effective."
An Ofsted spokesman said: "The reason the chief inspector is introducing 'requires improvement' is to make sure that all weaker provision is improved as quickly as possible."