A-level and GCSE grades in England will now be based on teacher-assessed grades, rather than by an algorithm, in a dramatic U-turn by the government.
The government announcement came shortly after Wales said it was reverting to teacher assessments for A-levels and GCSEs.
Ministers announced they were to scrap the controversial standardisation model drawn up by the exams regulator, Ofqual, to award grades in lieu of exams.
Ofqual chair Roger Taylor and Education Secretary Gavin Williamson apologised for the "distress" caused.
Mr Williamson 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.
"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
Earlier in the day Northern Ireland said its GCSE results would be solely based on grades provided by teachers, following a similar U-turn in Scotland last week.
In a tweet, Labour leader Sir Keir Starmer said the government had been "forced into a screeching U-turn after days of confusion".
He criticised Downing Street's handling of students' results as "a complete fiasco" and said its about-face was a "victory for the thousands of young people who have powerfully made their voices heard this past week".
Hundreds of pupils took to the streets of London, demonstrating outside the Department for Education to express their anger, while others took to the airwaves and social media to describe their sense of devastation, and lawyers began to consider taking action on behalf of affected teenagers.
Alistair Jarvis, chief executive of Universities UK, said universities were being "as flexible as possible with applicants" but that the "late policy change" has created "challenges" for universities.
He said: "Today's policy change will mean that more students will have the grades that match the offer of their first choice university. This will cause challenges at this late stage in the admissions process - capacity, staffing, placements and facilities - particularly with the social distance measures in place."
He called on the government to "step up and support universities through the challenges created by this late policy change", adding that Universities UK was seeking "urgent clarification" from No 10 on a number of issues.
Addressing concerns about capacity problems at universities, Mr Williamson said: "We are already working very closely with the university sector to make sure that we do everything we can do to build as much capacity in there.
The algorithm used by Ofqual for both A-levels and GCSEs was mainly based on a school’s past results and individual pupil attainment.
Ofqual argued the algorithm was essential to ensure results were standardised across the country and in line with previous years, but hundreds of individual stories documenting disappointment and an overwhelming sense of injustice among those affected proved too much to ignore.
Meanwhile, Manchester's metro-mayor Andy Burnham has praised young people and parents for protesting the government's A-level results policy while accusing the government of "casual discrimination" against working class children.
Addressing his comments at pupils, he said: "What I would say to them tonight is never ever let anybody tell you that these aren’t the right grades, or that these grades shouldn’t have been given to you. They are the grades you deserve because I know the efforts your teachers have made to make these assessments.