Peter Buchanan, headteacher at Dyson Perrins, in Malvern, is telling next year's A'Level candidates not to be distracted from their studies by the current row over grades.

His pupils' grades in history and computer science, already good anyway, are currently being looked at. Revised results are due to be issued on Tuesday (October 15).

Mr Buchanan said the credibility of the exam system had been dealt a massive blow and a lot of work would be needed to restore people's faith in it.

"I don't think the students should worry about the philosophical aspects of it now," he said.

"Teachers have to teach and students have to learn, and we all have to focus on the work.

"I don't think the same thing is going to happen next year, because the consequences would be so horrendous if it did."

Hanley Castle head Alan Johnston said: "I hope that next year everyone works together and it's made clear to teachers and students how the exams will be marked and how the grade boundaries will be set, so it's a level playing field and not subject to political considerations."