Schools will be able to view marked exam papers before deadline dates to challenge them for the very first time from 2020 under a shake-up of review procedures, examinations watchdog Ofqual said.
Exam boards will also have to explain their reasons for changing or not changing marks, and they will be required to ensure schools offer pupils the opportunity to have their coursework marks reviewed.
Ofqual says the changes, which will affect GCSE, AS and A-level pupils in England, will "deliver a clearer, more consistent, and fairer system for all students".
The changes were decided last year, but Ofqual has only now announced when they will come into force, following discussions over their potential impact.
Exam boards will be required by 2020 to make marked GCSE papers available to schools before deadline dates for reviews so they have time to assess whether they want to challenge the marks or not.
Currently, few exam boards return papers to schools before the cut-off point, meaning they are only able to submit a "blind appeal" as they do not receive graded papers ahead of the review deadline.
The change will bring review procedures for GCSEs in line with those for AS and A-levels, which already allow schools to see them before review deadlines.
Exam boards will also by 2020 have to explain their reasons for altering or not altering marks in GCSE, AS and A-level papers, a change from the current system in which they only have to say whether they are or are not amending results.
Boards will be forced to ensure that schools offer pupils the opportunity to ask for their coursework to be reviewed, a change that must be in place by the summer of 2018.
And the removal of automatic grade protection - changing the current rules that allow one student's marks to be protected if another's are regraded downwards - is being deferred for at least two years.
Julie Swan, Ofqual's executive director for general qualifications, said: "Today's decisions confirm key aspects of the timeframe for completing our changes to the systems schools and colleges use to challenge GCSE, AS and A-level results in England.
"In combination with the changes already announced and implemented last year, they will deliver a clearer, more consistent, and fairer system for all students."
Russell Hobby, general secretary of school leaders' union the National Association of Head Teachers (NAHT), welcomed the revamp.
He said: "NAHT has consistently called for greater transparency in exam marking and we welcome changes outlined by Ofqual today.
"We particularly welcome plans to ensure exam boards explain their marking in the case of challenged grades, and that students will receive copies of their marked GCSE papers without charge."
But he argued that, with one in five A-level and GCSE grades overturned when challenged, the system is still "fundamentally flawed".
He said: "The cost of challenging grades also remains prohibitively high for schools. With budgets being pushed to breaking point, many schools cannot afford to challenge unfairness. This is not right.
"We would like to see a fairer system for re-marking, including a fund to help schools pay for regrading. Challenging grades should not be based on the ability to pay, but rather a desire to address misjudgements in the grading process."