Teachers are telling pupils exactly what to write in GCSE coursework in their desperation to improve results, examiners confirmed this week.
Secondaries are providing youngsters with detailed guidance, specifying the points to be made in each paragraph and the quotations to use, Britain's second-largest exam board said.
The findings come amid continuing concerns about how some schools are reacting to the pressure to raise pupils' achievements.
In its annual report on English GCSE, Edexcel highlighted as "insidiously worrying" the issue of "teaching by numbers" in coursework, where pupils' work from a single school was very similar.
The report said: "In such cases, teacher guidance to candidates stretches what is acceptable to the limit (and beyond) by providing over-detailed essay plans.
"(These) specify what should go in each paragraph, including the points to be made and the quotations to be used."
Pupils were being put into a "straitjacket", the report warned. They would find it difficult to obtain higher grades, because it was clear that their work was not original.
There was a high risk that this type of work would be penalised, the report added. At least 100 teachers were investigated by the boards for malpractice last year, one board penalising 516 pupils for what their teachers had done.
Many pupils were also being over-prepared for the speaking and listening section of the exam, said the report. Yet, again, this was hampering their ability to gain top marks.
The warnings confirm the findings of a TES investigation earlier this year, which revealed that some teachers believed that cheating on coursework had become institutionalised, as staff bent exam rules in their attempts to drive up grades.
It also uncovered evidence of the kind of point-by-point assistance for pupils cited in Edexcel's report.
Problems of plagiarism were reported in other subjects. On business and communication studies, the Edexcel report said: "Overuse of the internet continues to be a problem for some candidates, especially those who make no effort to disguise what they have done."
Some pupils were submitting coursework which was "little more than copied notes".
Examiners said that in two subjects, geography and Urdu, some able candidates could not obtain top grades because their teachers had entered them for foundation papers, where the maximum grade obtainable was a C.
On religious studies coursework, Edexcel examiners said: "Teacher assessment is often very accurate, and there appears less attempt (sic) by assessors to look a little over-optimistically at their students' work, raising a few extra marks here and there.
"However, there are centres where assessment is thoroughly unsatisfactory, and here specific guidance and training may be helpful."