Teachers in Bedfordshire, Berkshire and West Sussex have sounded the alarm saying that many schools had reported an unexplained dip in results on a written paper - one of the three making up the Associated Exam Board theatre studies A-level.
Berkshire drama adviser Marigold Ashwell said: "The word is consistency and that is the bit which seems to be missing.
"We have been working hard in the drama world to establish that the A-level in theatre studies has academic rigour about it. What could be happening now has to undermine the actual exam itself." Now she is considering organising a national survey of results.
Advisers say they have noticed a dip in marks for the second paper, which asks students to answer on set texts.
In Berkshire, Mrs Ashwell first noticed inconsistencies last year. But she said early returns also showed dissatisfaction with the 1996 papers.
In Bedfordshire, English and drama adviser Simon Wrigley said: "I am holding a meeting because there seems to be this discrepancy, and people ought to see what it is; whether it's our fault and we need to be concerned. At the moment the picture is very unclear."
West Sussex drama teachers are also planning to discuss the exam after noticing a dip in marks for the second paper.
AEB spokesman George Turnbull said the board had been alerted but had found no problems with this year's results.
He stressed that an across-the-board dip in marks on one paper would have little effect on grades, and said some students had exceeded expectations.
He said: "The department is aware of what is happening at least in one county and has made some enquiries. They are quite happy that there is nothing which has affected paper two or any other paper."