An exam board has called for schools to be judged over a five-year period to account for volatility in exam results.
In a new study, Cambridge Assessment researchers Tom Bramley and Tom Benton claim that volatility in exam results can be caused by an array of factors other than teaching, marking or exam reforms.
Even when factors such as reliability of marking are removed, more than one in five schools experience fluctuations that the Headmasters' and Headmistresses' Conference would define as a "serious concern".
"When we've taken account of the variations which can be attributed to quality of marking and to the location of grade boundaries, surprisingly high levels of year-on-year volatility in exam results remain," Mr Bramley said.
According to the researchers, schools should therefore be judged over a period of at least five years instead of on an annual basis.
The study was welcomed by Robin Bevan of the Association of Teachers and Lecturers, who said it is important to judge the performance of those in teaching jobs on sound evidence.
Posted by Alan Douglas