New allegations that exam boards are deliberately lowering standards in order to increase their business will add to the controversy over league tables. Channel 4‘s Dispatches programme on Wednesday argued that competition between exam boards is leading to easier grades, and that schools are choosing exams which will place them higher in the league tables.

It presented evidence from a new research study, from disaffected senior examiners, and from several schools, showing that Government policy and its emphasis on competition was at fault.

The research, commissioned by Dispatches, shows that a third of students sitting maths GCSE papers from two different boards did better on one than on the other. It was conducted by Professor David Burghes, chair of maths examiners at the Associated Examinations Board and professor of education at Exeter University. He gave the exams to 400 students from across the country on the same day. Professor Burghes called the results “quite damning”.

He also described a “ratchet effect”, whereby a slightly easier award that would make little difference in one year could have a significantly greater effect over 10 years. Last year, hundreds of schools changed exam boards.

At Cheltenham College, an independent school, the number of A-C grades for the lower two sets rose by 75 per cent after the school switched from Oxford and Cambridge to the AEB for physics. The school remained with OC for its top set, which achieved all As.

George Turnbull of the AEB said there was no evidence to suggest that some exams were easier than others. However, other specialists said it could make a difference of one or two grades.

Dr Declan McCartan, former chief examiner for the Northern Ireland Council for the Curriculum, Examinations and Assessment, said that in 1990 his board had advised examiners for pure and applied maths to make the papers “more accessible and do-able”, bearing in mind an exam board across the water.

He said in this year’s awarding meeting the team felt they had to bring the grade A boundary down by about three percentage points in order to be fair to the candidates, so more Grade As were awarded than had originally been intended.

Keith Weller, assistant chief executive for key stage 4 at the School Curriculum and Assessment Authority, which polices public exams, wanted to know more about the methodology used in the research and said he would want to hear views of other examiners. Shopping around for the easiest board could look like a risky policy for a school, and if a board marketed a shoddy product, a poor reputation could stick. He said consistency between boards has been “a continuing concern since O-levels and A-levels were invented.” There were checks and balances, but SCAA still had to be vigilant.

Last year a SCAA inquiry found some boards had marked too leniently at grade B. SCAA and the Office for Standards in Education are conducting an inquiry into A-level and GCSE standards, commissioned by the Secretary of State. There is now a system of external assessors who visit different boards.

Richard Daugherty, professor of education at the University of Wales at Aberystwyth, said SCAA had been tightening up its procedures. “Ten years ago, when there was less concern, there was far more discrepancy in practice, ” he said. Comparisons were difficult, he said, but the system was intended to allow schools and teachers the freedom to choose the syllabus and content they wanted.

There were a variety of reasons for boards to change their grade boundaries. “I think the real issue is how far it’s being done for the wrong reasons and without very hard evidence it’s difficult to prove,” he said.