Welsh Education Minister Kirsty Williams has apologised “directly and unreservedly” for the way A-level results were handled last week.
There was outrage after 42% of A-level grades in Wales were downgraded.
On Monday ministers abandoned the system used to calculate the results, awarding assessments made by teachers instead.
Ms Williams said she was “truly sorry” for a process that made a stressful time “worse” for some students.
The minister made the apology in a social media video, and in evidence to a Senedd committee, a day after the U-turn.
“For our young people, and indeed everyone in Wales, the last few months have been and continue to be a stressful time,” she said.
“It has been a time of anguish for people right across the country.
“I am sorry that, for some of our young people, the results process has made that worse.”
“Recent months have thrown up unexpected, new and complex challenges,” she said.
“Working with Qualifications Wales and the WJEC we looked for an approach which provided fairness and balanced out differences in the standards applied to judgments in schools.
“But, as I announced yesterday, and given decisions elsewhere, the balance of fairness now lies with awarding centre assessment grades to students.”
The apology marks a change in tone from the First Minister Mark Drakeford, who said on Monday he was “sorry for those young people who’ve had to live through such an uncertain period”, but defended the system that had been used.
Some of his comments after the U-turn were dubbed “pretty shocking” by Blaenau Gwent Labour AM Alun Davies, in a tweet.
Ms Williams’ apology was the second that day from a Welsh Government minster, after Health Minister Vaughan Gething said he was sorry for any anxiety and stress caused.
UK government Education Minister Gavin Williamson has apologised for exam “distress” in England, where ministers have also moved to grades estimated by teachers. Similar decisions were taken in Scotland and Northern Ireland.
As well as A-levels, teacher assessed grades will be used for GCSEs, AS-levels, skills challenge certificates and the Welsh Baccalaureate.
Last week’s results in Wales were produced by a system known as standardisation – designed to ensure grades were “as fair as possible” and consistent with previous years.
But it was criticised by students and politicians for producing unfair grades for individual students. GCSE results are to be published on Thursday.
Minister learned of results impact on 10 August
The Liberal Democrat education minister told the Senedd’s education committee that she was not informed of the scale of the impact of using the algorithm to moderate A-level results until 10 August, three days before the results were due to be announced.
She said she had been told on that day that 42% of grades would be depressed.
“I was given those results on the 10th of August, and we were concerned,” she said.
Ms Williams said the Welsh Government was “particularly concerned” about whether there might be a “disproportionate effect” on pupils receiving free school meals and had asked for more data.
She said the WJEC supplied that information to Qualifications Wales the following evening, and it was given to her the morning after that – Wednesday – the day before the results came out.