A-level and GCSE students in England will be given grades estimated by their teachers, rather than by an algorithm, after a government U-turn.
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.
He said students and parents had been affected by "significant inconsistencies" with the grading process.
In a statement, he acknowledged the "extraordinarily difficult" year for students, after exams were cancelled due to the coronavirus pandemic.
He said the Department for Education had worked with Ofqual to design "the fairest possible model" but it had become clear that the process of awarding grades had resulted in "more significant inconsistencies than can be resolved through an appeals process".
"I am sorry for the distress this has caused young people and their parents but hope this announcement will now provide the certainty and reassurance they deserve," said Mr Williamson.
The education secretary told reporters No 10 does not get "any of the detailed data before schools do" but when it saw these "quite concerning outliers" they asked questions.
Mr Williamson said he hoped BTecs would be subject to teacher-assessed grades, and that the government was working with the "awarding authorities" to ensure this happened.
He also revealed the temporary cap on the number of places that universities can offer to students would be lifted.