National 5 exams will be cancelled in 2021 and replaced by grades based on alternative assessment and teacher judgment.
Education secretary John Swinney also announced that the start of Higher and Advanced Higher exams will be pushed back by two weeks to May 13.
In a statement to Holyrood, Mr Swinney said: “The virus is still with us, so we cannot plan for business as usual. That is simply not possible.
“Due to the level of disruption already caused by Covid, and due to the likely disruption faced by some or all pupils and students this academic year, a full exam diet is simply too big a risk.
“It would not be fair.”
During today’s statement, deputy first minister Mr Swinney again admitted the Scottish Government “did not get it right for all young people” this year.
Mr Swinney survived a vote of no confidence after pupils from poorer backgrounds protested that their results were unfairly downgraded in the 2020 results.
The fiasco resulted in an apology from First Minister Nicola Sturgeon and repeated calls from opposition parties for Mr Swinney to resign.
To avoid a similar muddle this year, Mr Swinney said that the SQA will today publish broad guidance on its evidence gathering and estimation for 2021’s results.
This will be followed after the October holidays by subject-specific guidance on the key pieces of work young people will need to complete.
Mr Swinney said: “First and foremost, awards will not be given – or taken away – on the basis of a statistical model nor on the basis of a school’s past performance.
“There will be no algorithm.”
Today @JohnSwinney confirmed plans for SQA awards 2021
🔷Higher and Advanced Highers exams will go ahead if safe to do so, with contingency plans developed
🔷National 5 exams to be replaced with awards based on coursework and teacher judgement
Read more: https://t.co/Ic3REsadv6 pic.twitter.com/O7qbj5Oult— ScotGov Education (@ScotGovEdu) October 7, 2020
Work towards the following year’s exams usually begins in May but as schools were still closed, pupils lost out on at least two weeks of study.
The later start date for Higher and Advanced Higher exams is designed to compensate for this.
Replacing National 5 exams was recommended by Professor Mark Priestley in an independent review into the events following the cancellation of exams in 2020.
Mr Swinney said: “By replacing  National 5 exams, we can hold an exam diet for Highers and Advanced Highers if public health guidance allows – these are the qualifications most pupils leave schools with that determine paths into work, college, or university.
“None of us can predict the coming weeks and months, so clear contingency plans are being developed should, for public health reasons, the exams have to be replaced.”
Opposition parties at Holyrood are not convinced that National 5 exams should be cancelled for 2021.
Scottish Conservative education spokesman Jamie Greene said: “A full exam diet could and should take place next year.
“The onus was on the education secretary to make that happen or instead justify why that cannot be achieved under his watch.
Labour’s Iain Gray added: “The truth is this statement is very, very late.
“Teachers are months into teaching courses without knowing exactly what they should be teaching, how pupils will be assessed and what evidence they should have been gathering.”