TWELVE years ago a 15-year-old had to get a mark of 65 per cent to get a C grade in the intermediate-level paper in GCSE maths. This year, a C could be earned with 45 per cent. In the higher-level paper, just 18 per cent would get a C.

This is clear evidence of grade inflation, according to Jeffrey Robinson, who has just retired as a principal examiner with the second biggest exam board, OCR. He poured cold water over last week’s GCSE celebrations with claims that grades in the exams taken by more than a million students had been fixed.

The indignant exam board, which hastily rounded up 13 senior examiners to refute the claim, insists there is an explanation for the apparent lowering of grade boundaries.

In 1989, students sitting the intermediate paper could score from C to G and had a choice of questions. Crucially, there was no rule that strict proportions of questions had to be aimed at different ability levels.

Now, papers must provide a set proportion of questions aimed at each level. So in the intermediate paper, covering B, C, D and E grades, a quarter of the marks are for questions at E-grade level, a quarter at D-grade and so on. A C-grade student should therefore be able to tackle 75 per cent of the paper. In the higher paper, covering A*, A, B and C, a typical C-grade candidate would only be able to answer 25 per cent of the questions.

A student achieving the grade has to get roughly two-thirds of the marks accessible, so the C-grade boundary was set at 45 per cent for the intermediate exam and 18 per cent in the higher exam. Our chart (above) does not support Mr Robinson’s claim that the pass mark has been lowered every year.

Maths experts have criticised the premise of a system which awards a good pass on the basis of less than a fifth of the overall marks.

Steve Abbott, president of the Mathematical Association, said:“C grade candidates at higher level are picking up a few marks here and there and not necessarily showing depth of understanding.”

Tony Gardiner, reader of maths education at Birmingham University, said it was a ridiculously fragmented approach which made the GCSE like an MOT test.

Maths papers are also harder, exam boards claim. In 1989, for instance, the intermediate paper would have given a student four marks for drawing a bar chart. Now bar charts are classed as too easy and have been relegated to the foundation paper.

According to Tony Millns, former assistant chief executive of the Qualifications and Curriculum Authority, setting the right level of question is all-important as large increases or decreases in grade boundaries undermine faith in standards. “Big changes (in grade boundaries) indicate that the exam was not well set. It does not mean that it was fixed,” he said.

Inevitably exam content changes over time. The national curriculum was revised in 1995, leading to changes in GCSEs.

The curriculum has also broadened over the years. In foreign languages O-levels, for instance, students had to have good grammar skills but only 3 per cent of the exam was oral. Students today might have poorer grammar, but are much more proficient in the spoken language.

These changes allow the exam boards and the QCA to argue that you cannot compare apples and pears, and that exam papers are different, not easier. But industry is convinced that grade inflation occurs. And universities claim standards are dropping.

The controversy has prompted calls for a simpler, more transparent grading system. Professor Ted Wragg, a QCA board member, said: “A pass mark of 18 per cent seems extraordinarily low. It is difficult to understand or know the inside story.”

Ron McLone, chief executive of OCR, said the workings of the exam system were far from secret. However, when The TES asked for grade boundaries going back to 1994, it was told that only the last four years were available on computer records.

Fears of grade inflation in the early 90s led to an inquiry by the Office for Standards in Education and the forerunner to the QCA which found standards in maths, English and chemistry A-level over 20 years had remained broadly in line.

It has been followed by five-yearly rolling reviews of individual subjects by the QCA. But reports on standards in GCSE English, chemistry, physics, biology, German and history from 1995-99 have still not been published.