Comments from the BBC Education correspondent:
"This decision in Scotland puts the cat among the pigeons for exam results for the rest of the UK - where A-level results are due on Thursday.
If Scotland's students are given higher grades based on teachers' predictions, how will it be fair if they're competing for the same university places as students from England, Wales and Northern Ireland?
Will the newly-boosted grades of Scottish students bump others out of university places, whose results have been pushed down by the moderation process?
And if pegging pupils' results to the previous achievement of their school is unfair in Scotland, how will it be fair for those getting A-levels in England, Wales and Northern Ireland.
These grades are for life, important for jobs as well as higher education. And it raises the question which is more important, fairness for the individual, or the smooth running of the exam system?
Scotland's change of heart will pile on the pressure for changes in the rest of the UK - but like turning an ethical Rubik cube - any change will generate other patterns of unfairness.
In England using teachers' predictions would have meant almost 40% getting an A* or A at A-level this year - and below that average there will be some teachers that have been very tough and others very generous. That would risk creating even more inequalities that could fill court rooms for years.
Until now England's Department for Education has rejected any change of plan, but the stakes have been raised."