The exams watchdog Ofqual is struggling to link school exam results to teaching quality, its chief regulator has admitted.

Sally Collier told a group of politicians and academics this morning that she was “finding it very difficult” to say to what extent rises and falls in GCSE and A level results were down to better teaching or other factors.

It follows a period of widespread reform of curriculum and assessment in England, designed to limit grade inflation and ensure the proportions of pupils achieving top grades remained roughly consistent year-on-year.

Critics of the changes have said that the changes – known as comparable outcomes – mean genuine improvements in teaching are now difficult to discern.

Lord O’Shaughnessy

During a session on educational standards chaired by academy trust founder, Lord James O’Shaughnessy, Collier said schools were “rightly saying” they wanted to attribute recent rises in GCSE and A-level results to better teaching.

“I’m finding it very difficult to disentangle when the results go up or down to what extent it’s to do with better teaching,” she said. “We’ve published some research last week that says when you introduce a new curriculum, when you make all these changes, there is an impact on results.”

Last week Ofqual released a report into the ‘sawtooth effect’ of assessment reform, which revealed the regulator could not separate increases occurring in test results from those which are due to familiarity with the subject and genuine improvements in ability.

The report noted that as teachers become experienced in teaching the contents of a particular exam, results increase. When exam papers are changed results tend to tumble initially before climbing again – creating a ‘sawtooth effect’.

At the event, Collier accepted criticism from several delegates, including O’Shaughnessy, of the current system of standards faced by schools.

In response she said that some aspects of exams were still “imprecise and then we pin all our accountability measures on it” which caused “unnecessary tension in the system”.

An Ofqual spokesperson said the challenge of unravelling the factors influencing results were “well-documented, including in our own recent research”.

The introduction of national reference tests for 16 year-olds this year is designed to help with the puzzle.