It follows uproar after about 40% of A-level results were downgraded by exams regulator Ofqual, which used a formula based on schools’ prior grades.
GCSE results in England, Wales and Northern Ireland come out on Thursday.
Ofqual chair Roger Taylor and Education Secretary Gavin Williamson apologised for the “distress” caused.
Teachers’ estimates will be awarded to students unless the computer algorithm gave a higher grade.
Mr Williamson said the results of mock exams – which critics said can be inconsistent across different schools – will now not be a key part of the appeals process.