AN education think tank is urging pupils to take rigorous backup assessments rather than relying on mock scores in case next year's exams are scrapped.
A-level, AS-level and GCSE exams are due to go ahead in the summer but young people will sit fewer papers.
Unions have been demanding that ministers look at contingency planning.
In Wales, Education Minister Kirsty Williams is due to announce 2021 exam arrangements in the Senedd on Tuesday.
The Welsh Government commissioned a review which called for all exams to be scrapped.
Now, a report by the Education Policy Institute (EPI) has said teacher-assessed grades should be avoided until there is more evidence about their reliability and their impact on disadvantaged pupils.
In it, the EPI has called on the UK government to urgently set out a "backup plan" in the event that summer exams are cancelled.
It said a new series of benchmarking assessments should be introduced to provide "contingency grades" if papers cannot take place.
These assessments, which would be set by exam boards and taken in the spring term, would replace existing mock exams.
The EPI said this would provide "greater consistency than traditional mocks".
The recommendations follow the fiasco around grading of GCSE and A-level pupils this summer.
"There is a strong case for changes to exam papers, to enable pupils to be assessed on the content that they have actually covered this year," said David Laws, executive chairman of the EPI.
"We also have to be prepared for a scenario in which next year's exams cannot take place. To do that, the government should consider using more formal 'contingency assessments' in place of the usual mock exams, which students can then use as backup grades.
"It should avoid falling back on predicted grades again, as questions remain over their reliability. Pupils will face huge challenges to their education this year, so we must have a system that is fair. We cannot see a repeat of the turmoil that we had in the summer."
Exams regulator for England, Ofqual said it was continuing to discuss contingency options for all likely scenarios. Thousands of pupils from Northern Ireland take GCSE and A-levels set by boards in England.
"We expect to provide advice to the government to enable it to determine and confirm contingency arrangements for 2021 with the sector this month," Ofqual said.
It added that it was also considering ways to make the prospect of exams "less daunting" for those who have missed out on teaching and learning.
