HEADTEACHERS last night demanded a Government commission into exam standards to finally put an end to accusations that they are getting easier.

As thousands of students celebrated their GCSE results yesterday, a former principal examiner claimed political and commercial pressures had made it easier to score top grades.

Jeffrey Robinson, 67, who has just retired from the Oxford, Cambridge and RSA Board, one of the three main exam boards in the country, said students taking the maths paper this summer could now get a C grade with a score of only 18 per cent.

He said he had sat in meetings to decide grade thresholds and watched them being reduced year on year.

Candidates had to score 65 per cent to get a C grade in 1989, while last year 45 per cent was enough, he said. This year, in the case of the higher level paper, the threshold had been cut from 48 per cent to 18 per cent.

"The levels at which the thresholds are drawn between grades have come down very significantly," he said.

"They are effectively as much as 50 per cent lower in the case of C grades than they were in 1988.

"People who now get a grade C really know little algebra at all. Basic things like percentages are almost beyond them. Those who creep on to a C grade really know little maths at all."

But his comments caused an outcry across the region as teachers were yet again forced to defend their hard-working pupils.

There were also angry reactions from the Government, exam boards and the teaching unions.

Terry Bladen, a teacher at Eastbourne Comprehensive School in Darlington, and junior vice-president of the National Association of Schoolmasters/Union of Women Teachers branded Mr Robinson's comments "pathetic".

"It seems to be a thing with this country to knock success. We can't just accept it for what it is," he said.

"Exams are different - not easier. At one time, all they did was test memory but now it's how you apply what you have learned."

David Hart, general secretary of the National Association of Head teachers, said there needed to be an urgent report from the exam boards, the Joint Council for General Qualifications, and the Qualifications and Curriculum Authority (QCA) on exam standards.

"We really can't have this debate every year. It is becoming wearying and it cannot help the morale of teachers and students," he said.

"It is the duty of the department to call on the exam boards, the joint council and the QCA to report to ministers with the utmost urgency so that students and their teachers can be reassured and we can get away from this annual education standards-bashing, which is becoming utterly unacceptable."

Dr Ron McLone, chief executive of exam board OCR, said it was "always a shame when retiring examiners vent their spleen".

"Nearly 50 years ago, only one person ran the mile in under four minutes," he said.

"Today nearly all serious milers can do so, but the mile is still a mile. Students who get a grade C on the higher tier have to tackle the most difficult questions. The marks they get reflect that."

A spokeswoman for the Department for Education and Skills said: "We wholeheartedly reject this claim, which is a slur on the achievements of young people."