Exam board Edexcel is again being pilloried for having made errors - but it is not alone.

The UK's biggest exam board, AQA, set GCSE English literature students at 25 centres questions about poems that had not been in their syllabus.

Its spokesman, George Turnbull, has been seeking to explain the standard reassurance from exam boards that "no students will be disadvantaged" as a result of blunders of this sort.

For one thing, he says, errors are neither new nor getting worse - the problem is that we now have 24-hour "rolling news" as part of the entertainment business, hyping the issue.

But, admitting "huge embarrassment" at his own board's error this week, Mr Turnbull accepted that the upset caused to students who came across an error while sitting an exam could be out of all proportion to the value, in marks terms, of the particular question involved.

Individual reviews

"Some of the things we have seen recently have been questions which are worth one mark," he said.

"Students are trained to spend only an appropriate amount of time on a question, and if you can't do it to leave it. The majority will do that.

"But the chances are there will be one student who is caught on it and spends a lot of time on it or will worry because they can't do it. We are all affected differently."

In such cases it was up to schools or colleges to apply for "special consideration" by examiners.

The procedure was essentially the same as for anything else which might affect a candidate's performance - such as being ill on the day or having a relative in hospital or being in an accident on the way to the exam.

"If a school tells us a student was affected and, say, lost half an hour, that would be looked at individually."

Only human

In judging their likely performance exam boards could also draw on students' predicted grades, coursework and perhaps other exam results in the subject.

"We have a whole department here just dealing with special circumstances all the time," Mr Turnbull said.

Examiners were aware of the issue.

"They have got relatives themselves in some cases who are sitting examinations, and have sat exams themselves.

"It's unfortunate when mistakes happen, but we are not superhuman.

"Standards in the UK are extremely high - unequalled."