The Scottish Qualifications Authority has sought to play down the departure of six senior examiners over the marking of last year’s Higher maths exam.

The principal assessor, who has not been identified, had his contract terminated and the move prompted a walkout by five of his colleagues - a senior examiner and four exam setters.

It is understood they had concerns around a drop in the 2012 pass mark - from 63 out of 130 to 62, leading to a slight increase in the pass rate rather than the original dip.

They are also understood to have raised concerns over the reliability of future Higher maths exams, suggesting that it might be adversely affected by having a less experienced marking team in place.

SQA stressed that variations in pass marks are not intended to boost pass rates, but to ensure that the difficulty of the Higher remains the same each year.

Gill Stewart, director of qualifications development, explained: “In 2012, the grade boundaries for Higher maths were adjusted to reflect a few questions at the end of Paper 2 that proved to be more demanding than expected.

“This decision was made on the basis of clear statistical evidence. In addition, SQA had received similar feedback about the exam from around 800 candidates and 80 teachers.

“SQA is satisfied that the grade boundaries for Higher maths were set appropriately to ensure that a candidate who would have achieved a ‘C’ grade in 2011 would also get the same grade if they had sat the 2012 exam.”

Dr Stewart said the SQA had “full confidence” in this year’s “strong team of experienced appointees”.

Chris Pritchard, chair of the Mathematical Association’s teaching committee and editor of the Scottish Mathematical Council Journal, acknowledged “a loss of experience on a very considerable scale”.

He added: “That said, there is no shortage of replacements capable of meeting the challenges over the coming months.

“I’m sure that the SQA will take considerable care to ensure that what is certainly a difficult situation is handled so as to minimise any adverse effect on candidates.”

Dr Pritchard continued: “What is surprising is that there should have been such a coming to blows over the adjustment of the threshold by a single mark, a change affecting only a relatively small number of candidates. Of course, the whole issue of the difficulty of examination papers and the fixing of the pass mark and grade boundaries is, and will remain, rather thorny.”

Ken Cunningham, general secretary of School Leaders Scotland, said he did not believe there was wide-ranging concern about Higher maths marking.

He said he was was “absolutely sure” the SQA would do its best to ensure future exams went smoothly with the new team members in place.

henry.hepburn@tess.co.uk.