Results released by the SQA earlier on Tuesday show another year in which the attainment gap between the most and least deprived pupils had widened.
They also show an overall drop in pass rate across National 5s, Highers and Advanced Highers, as well as one of the highest rates of A grade passes recorded.
The figures come after a year of controversy and scrutiny around the SQA and the Scottish Government’s approach to qualifications, with concerns raised about pupils sitting exams “in all but name” and an appeals service labelled not fit for purpose.
The Scottish Liberal Democrats said the figures showing a widening of the attainment gap made a “mockery” of SNP promises.
The party’s education spokesperson Beatrice Wishart said it was time for chief executive of the SQA, Fiona Robertson, to step aside to allow the planned reform of the quango to go ahead.
She said: “Pupils were forced into exams in all but name, sitting as many as 16 assessments in a week, crammed in with little notice.
"The SQA shifted workloads onto teachers and gave them precious little leeway to recognise that some of their students had missed months of education due to repeated stints in isolation or disruption at home.
“The fact that the gap between the richest and the poorest has increased again make a mockery of SNP promises to close the attainment gap. The blame for this sits firmly with the government and its education quangos.
“After years of putting their fingers in their ears, the Scottish Government eventually conceded that the SQA isn't fit for purpose, but only after Parliament backed the Scottish Liberal Democrats in a vote that piled pressure on ministers.
"With this year’s process drawing to a close, and still repeatedly refusing to apologise for last year's debacle, Fiona Robertson should step aside and allow that reform to take place.”
Scottish Labour said the system for 2021 had failed the poorest pupils, blaming a “total lack of leadership” in Scottish education.
Last year, thousands of grades were downgraded by the SQA, forcing an embarrassing U-turn from then-education secretary John Swinney following an agreement with the Scottish Greens on the eve of a no-confidence vote in the minister.
Exams for National 5s were cancelled in October, with Highers and Advanced Highers cancelled in December 2020.
Mr Swinney was later sacked from his role and replaced by Shirley-Anne Somerville after the election, with the new Cabinet secretary sticking to the plans laid out by her predecessor.
Michael Marra, Labour’s education spokesperson, said students and teachers had performed “nothing short of miracles” in a disrupted year.
He said: “Scottish education has suffered from a total lack of leadership this year. We see this in everything from the late cancellation of exams, to the shambolic roll out of the ‘alternative certification model’ [ACM], to the appeals system which took none of this year’s extraordinary circumstances into account.
“This system has widened the educational attainment gap in Scotland, meaning that poorest pupils have been impacted the worst by the SQA and Scottish Government mismanagement.
“The result is that there are many young people, particularly in our poorest communities, who have not achieved the grades they had hoped or deserved.
“The government should implement a ‘re-sit guarantee’ without delay, and offer a further education place to any young person impacted by the disruption of the pandemic who wishes to re-take their subjects.”
Reacting, the Scottish Greens said the moderation system in place in which councils and schools were asked to compare results to previous years was the reason behind the widening of the attainment gap.
Ross Greer, the party’s education spokesperson, said: “Just like last year’s postcode-based moderation system before it was reversed, this year’s grades were adjusted against previous results at each school. It’s therefore not a surprise that the attainment gap has widened.
"After all, the restored grades from last year, when the attainment gap dramatically narrowed, were excluded from this moderation system. This intense suspicion of working-class young people who achieve just as much as their middle-class colleagues shames Scotland.
“The purpose of education is to enable every young person to reach their full potential, not to sort the world into haves and have-nots based on where they live. The SQA’s leadership have again failed to understand this basic idea.”
Larry Flanagan, general secretary of Scotland’s largest teaching union the EIS, said lessons would be learned around the implementation of the alternative certification model, but praised teachers and pupils.
He said: “The additional pressure and workload created by the late move to adopt the ACM, compounded by a three-month lock-down, placed a particularly heavy burden on teachers and lecturers, and they deserve sincere thanks for their absolute commitment to ensuring that young people could receive the grades that they deserved.
“As we look ahead to the welcome replacement of the Scottish Qualifications Authority and a refresh of a qualifications system that still places too much emphasis on high-stakes, end-of-year exams, there will be lessons to learn from this year’s experience.
"Today, however, is about recognising and celebrating the successes of Scotland’s young people.”
David Lott, the deputy director of Universities Scotland, said the results had the confidence of its institutions.
He said: “Demand for university remains very strong from our Scottish-domiciled applicants as well as from the rest of the UK and internationally.
"Universities are very pleased to be able to accommodate much of this demand this year following the creation of additional funded places for Scottish students.
"The UK is about to see a demographic trend towards a sharply growing number of 18 year-olds and this, combined with high levels of success amongst school leavers, will add to future pressure on places.
“Students starting next month should be reassured that universities have confidence in the integrity of the teacher assessed grades. The resilience and determination shown by this cohort of school and college leavers will stand them in good stead for both their academic career and life beyond university.”
A SQA spokesperson said: “Today is not about SQA or any individual. It is about celebrating the achievements of learners right across Scotland.
“There is a review underway looking at the replacement of SQA and a debate to be had about the future of assessment, but today let’s recognise the hard work of 137,000 learners who have received their certificates.”