The Edexcel board, which offered a maths exam this summer in which pupils could score an A grade in two papers with scores of just 45 per cent, is to make the tests more "accessible". Grade boundaries could rise as a result.
A report on the exam by Edexcel's chief examiner's said that syllabus changes ordered by the exams regulator, designed to encourage more lateral thinking among candidates, have made the papers more difficult.
Those changes, introduced last year, meant more questions set in real-world contexts, under "Using and Applying Mathematics", and unstructured problems, in which pupils are not led to an answer.
Edexcel argues that the wording of questions, and the fact that some teachers had not prepared pupils for some new topics, also made the papers harder.
It compensated this summer, by lowering grade boundaries. They were also lower in 2003 than in 2002.
The report says: "The integration of Using and Applying Mathematics and our need to meet new criteria in terms of unstructured questions has led to some papers becoming more demanding for candidates.
"Regrettably this has had the effect of reducing the accessibility of the papers, and we are sympathetic to some reports we have received that raise issues related to difficulty.
"We will be responding to these issues with urgency, and accessibility will be given a priority for the writing of future papers, including those for next year."
Some teachers have welcomed the move. Rosemarie Frost, from a leading private school where most students usually achieve top grades, said: "Some of the questions were harder than you would find at AS-level."
But Barbara Ball, professional officer of the Assocation of Teachers of Mathematics, said: "Edexcel is worried that schools are going to stop doing its exams because of the difficulty of the papers."
Tony Gardiner, reader in maths at Birmingham university, said: "As long as there are competitive exam boards, it is hard to see how anyone can ever drag standards upwards."
One leading examiner argued that boards faced a tricky situation. Changes required by the Government could make papers harder. But grades were supposed to be of equal value every year.
England's two other boards, AQA and OCR, said they were happy with their maths papers this year.
The Qualifications and Curriculum Authority said that making a paper more "accessible" did not mean making it easier. A question could be changed so the wording was more understandable, even though the maths behind it was the same level.
An Edexcel spokesman denied that the board believed that the paper was harder this year. He said the wording for some questions may have been less easy for some pupils to understand.
He added: "The exam will not be made easier. But we will try to ensure that it is as accessible as possible, so that it is clear from the context (of the question) that students understand exactly what's required of them."
1 (a) Express 108 as the product of powers of its prime factors.(b) Find the highest common factor (HCF) of 108 and 24.
2 Bill said that the line y=6 cuts the curve c2+ y2 = 25 at two points.
(a) By eliminating y show that Bill is incorrect. (b) By eliminating y, find the solutions to the simultaneous equations:
c2 + y2 = 25. y = 2 x - 2. edexcel 2004 paper