Head teachers' leaders are calling for a review of the examination system in England, following more well-publicised blunders by exam boards.

The general secretary of the National Association of Head Teachers, David Hart, has again called for one board, Edexcel, to have its licence revoked - as has the Liberal Democrat education spokesman, Phil Willis.

The leader of the Secondary Heads Association, John Dunford - representing a majority of secondary head teachers - does not share that view.

But all agree the whole exam system has become overloaded.

This week Edexcel admitted that some versions of a government and politics AS-level contained misleading information about the number of MPs at Westminster.

Delayed start

And the board asked Vocational A-level candidates to answer all the questions on a business studies paper, noting "there are nine questions".

There were actually 11 questions. The error was noticed by the board and erratum slips were sent out in advance by registered post.

We have used the board for many years and have been happy with their service

Roedean on Edexcel

Now it has emerged that sixth formers at girls' public school Roedean, in East Sussex, had to start their Edexcel biology AS-level an hour late on Monday because the papers had not arrived.

A courier sent with a spare set also did not turn up - and in the end the exam was faxed through.

But Roedean has said it is happy with the service it gets from Edexcel and has had problems with other boards in the past.

Edexcel's new head of external relations, Frank Wingate, said Mr Hart's comments were "unhelpful" and contributed nothing to the smooth working of the system - and the wider debate that needed to be held.

"All such comments achieve is to raise anxiety levels further at a time when students are already under pressure," Mr Wingate said.

On probation

Mr Hart first called for Edexcel to be sacked in January, following reports of errors in AS-level papers.

The Education Secretary, Estelle Morris, demanded action and the exam regulator, the Qualifications and Curriculum Authority (QCA), gave Edexcel a month to pull its socks up.

The time has come for the whole examination system to be revisited

David Hart

It subsequently decided that the board had put in place better systems.

But Mr Hart said of the latest mistake this week that it was "the umpteenth time" that Edexcel had "been found guilty" of errors.

"This level of incompetence wouldn't be tolerated in any other organisation," he said on BBC Radio 4's Today programme.

"They have been on probation for quite a long time. I think this is the end of the story.

"The QCA will have powers to take away their licence when the Education Bill gets through Parliament. I think those powers should be exercised."

Wider review

"We are over-examined anyway but we have to have a system in which schools can have confidence and we haven't got a system of that nature with these errors," he said.

"The time has come for the whole examination system to be revisited and to be run as an efficient operation without pressure and strain on students who are already under enormous pressure during the examination season."

The Shadow Education Secretary, Damian Green, said ministers had let things drift for too long.

"As well as considering the future of Edexcel, we should be asking questions about the role of the QCA which is meant to be regulating the exam boards and which seems to be presiding over a succession of scandals," he said.

The Department for Education said it looked to the QCA, as regulator, to ensure that all the exam boards met the high standards students and parents expected.

Phil Willis, Liberal Democrat education spokesman, said Edexcel was "fast becoming the Railtrack of the examinations system".

"It is time for the government to withdraw the examination contract from Edexcel, and to set up an independent inquiry into the UK's examination system."

System under strain

But the general secretary of the Secondary Heads Association, John Dunford, said the call for Edexcel to lose its licence was not widely supported in secondary schools.

"We look for a higher quality of performance from Edexcel, but the closure of one of the three examination boards would place greater stress on the other two boards and create disruption and discontinuity for schools," he said.

But the whole system was "at breaking point".

"The widely reported errors in examinations are an indication as much of the pressure on the whole examination system as the inefficient administration of one or more examination board.

Internal assessment idea

"We have far too many external examinations in this country and the system is in urgent need of a major review."

Dr Dunford has previously advocated having fewer external examinations and more internal assessments by teachers.

His association wants to see "chartered examiners" - senior professionals charged with upholding the standards of qualifications in their schools and colleges.

The idea that teachers might do more of the assessment has been echoed by the chief executive of Edexcel, John Kerr, as a way of addressing the shortage of examiners which all exam boards are experiencing.

How others do it

In some countries there are no examinations like A-levels.

In Germany, examinations are conducted and marked within the school - although increasingly they are set externally.

Assessors, usually from other schools, make checks on the marking.

In the United States, schools have much greater freedom in designing their curriculums and conducting assessments.

Universities combine the school test results with those from commercial admissions tests, the main ones being the SAT and the ACT - although experts say these add relatively little to the school grades on their own.

Two Australian systems - those in Queensland and the Australian Capital Territory - have no external examinations.

Individual schools' assessments are scaled in a way that makes them comparable across all schools.

The QCA has just appointed an Australian as its new chief executive.

He is Dr Ken Boston, currently director general of education and training in New South Wales.