An exam board is hoping to profit from a pound;100-a-year software product intended to help pupils complete coursework for one of its GCSEs.
Edexcel is advertising a program which, according to a teacher quoted on its website, "has the potential to revolutionise" the teaching of statistical aspects of GCSE maths.
Teachers have said the "valuable" new tool, which goes on sale for pound;99 plus VAT, in January, will help them cope with one of the least popular aspects of the subject.
But Dr David Burghes, director of Exeter university's centre for innovation in maths teaching, said: "Edexcel should not be involved in this. If it's worthwhile, every school should have it for free."
The tool has been designed by Edexcel's chair of examiners to support pupils with their coursework in data handling, which has been beset by problems since it was made a requirement last year.
Schools buying the product get a licence to use it for one year, after which they will have to pay to renew it. Edexcel's product will help schools and pupils without giving candidates an unfair advantage, said Rob Summerson, head of maths at Wootton Bassett secondary, Wiltshire. He said:
"It will ask pupils, for example, whether they want to deal with material qualitatively or quantitatively, but it will be up to the pupil to make that choice.
"It's like having a teacher in the room asking these questions. It's not inappropriate for a teacher to be doing so, so we don't think it's a problem for a computer program to be doing it."
Dr Burghes said he understood the program was very good. But the board, a profit-making organisation, should not be charging for it. He said the cost could disadvantage pupils from underfunded schools.
Exam boards have also come under fire for boosting their income by publishing textbooks and running pre-exam conferences for students with senior examiners.
An Edexcel spokesman said: "We think this is extremely good value. pound;100 is really only a nominal fee, reflecting the fact that it takes time and money to develop a product like this. The tool will not do the work for students - they still have to make all the decisions for their coursework.
We view this as an extra service which enhances what we do, and what schools and colleges do."
The board would make a profit on the software if it sold well, he added.