The warning comes after the exams watchdog wrote to a school saying it had published “unacceptable” GCSE essay templates on its website.

The Qualifications and Curriculum Authority is contacting headteachers’ organisations, Ofsted and local authorities highlighting its concerns over the use of the popular templates. QCA guidance says the frames can be used for practice tasks but the work submitted for assessment should be “completed independently by candidates”.

Isabel Nisbet, the QCA’s director of regulation and standards, wrote to The Ashcombe School in Dor-king, Surrey, criticising a GCSE English literature essay template on its website. The template, since removed from the main site, helped pupils write about the opening scene of the film Saving Private Ryan.

Ms Nisbet was alerted to the template after it was highlighted in Education by Numbers, a book by Warwick Mansell, a TES reporter.

She wrote to Ashcombe School’s headteacher, David Blow: “In the view of the AQA, JCQ and QCA, writing frames of the kind provided for Saving Private Ryan go clearly beyond the kinds of general prompts towards assessment criteria which are acceptable, because they are clearly specific to the particular task set and prompt candidates to use judgments already made...

“It is difficult to imagine how the responses of an entire class could differ at all when the candidates are required to follow a frame that directs the essay almost sentence by sentence.”

She added that the school was “by no means unique” in its error.

Mr Blow replied that his school did not use prescriptive writing frames and no longer studied Saving Private Ryan. He said he would welcome a visit or advice from the QCA or exam boards.

The templates, developed in the early 1990s to help pupils structure their thoughts on non-fiction texts, were initially used to aid younger children but are now used widely up to GCSE and A Level, and the rules, laid down by the Joint Council for Qualifications, are open to abuse.