A leading exam board is offering teachers monthly tips on how to prepare their pupils for GCSEs.
In what is believed to be the first instance of a board supporting day-to-day teaching for an exam, Edexcel is marketing a new series of regular bulletins for business studies teachers.
The board said the service was already proving popular, with more than 300 teachers signed up to it. It said the advice from examiners and supporting materials would enhance and enliven lessons.
But Ted Wragg, TES columnist and emeritus professor of education at Exeter university, described the move as "appalling".
For pound;42 a year, secondary schools are being offered the chance to subscribe to monthly email updates written by Ian Marcouse, a former chief examiner for business studies A-level at the AQA board and now chair of strategy for Edexcel business education.
Edexcel promises on its website that the email will provide high-quality, topical materials for immediate classroom use.
Among the features listed are GCSE classroom activities, a scheme of work with references to materials needed to support teaching, and reviews of new textbooks. The service also offers monthly updates from senior examiners and moderators.
Edexcel became the first major board to be run for profit when it was taken over by the Pearson publishing group two years ago.
Professor Wragg said the email advice was evidence that commercial pressures were influencing classroom practice.
"I'm absolutely appalled," he said. "Once you start getting the examination system driving the curriculum, frankly you strangle the curriculum. Pupils are told this is what you need to get you good marks, this is what questions you need to concentrate on.
"The curriculum, not the assessment system, should come first."
But Edexcel said the updates enriched teaching, and argued that the new service allowed teachers to include topical business case studies and other ideas for teaching.
It highlighted a written case study for pupils, sent out this month, on the success of Apple's iPod music-player, an updated scheme of work for the exam and advice from an examiner on teaching resources.
A spokesman said: "The idea that this is narrowing the curriculum is a total non-starter."