INSPECTIONS worsen pupils' exam grades at mixed comprehensives, research by Newcastle-upon-Tyne University suggests.
Its findings are based on an examination of the results of more than 3,000 schools inspected by the Office for Standards in Education.
Researchers found inspection had a "consistent, negative effect" on achievement at mixed comprehensives, which tended to see half a percentage point fewer pupils gaining five A* to C grades at GCSE than they should expect in the year a school was inspected. The effect persisted.
In mixed selective schools, girls' comprehensives and mixed secondary moderns results improved by up to 2 percentage points after inspection.
The report's authors said that, as most state schools were mixed comprehensives, the findings undermined claims that inspections help raise achievements. "Given these results, Ofsted has little value as far as most schools' GCSE examination performance is concerned," they wrote.
They added that, although their research was based on results from 1992 to 1997, they were doubtful that changes to inspections since then had made any difference.
The research is not the first to suggest that routine Ofsted secondary inspections fail to improve results. Researchers from Huddersfield University made similar findings in 1998, as did Philip Hunter, then Society of Education Officers president and now the chief schools adjudicator, in 1997.
John Dunford, general secretary of the Secondary Heads Association, said:
"The preparation for an Ofsted inspection can make a school take its eye off the ball. Inspections also tend to leave people in a state of exhaustion afterwards, and it is difficult for head teachers to pick up the pieces."
Ofsted figures show a year-on-year improvement in the quality of teaching since its launch in 1993. At Ofsted's 10th anniversary in November, chief inspector David Bell said the service had contributed to school improvement, but could not take any credit for rising test results.
"Do Ofsted inspections of secondary schools make a difference to GCSE results?" is in the British Educational Research Journal, Vol 29, No1