Details of a new examination regime to replace GCSEs are to be announced in the biggest overhaul of secondary school testing for a generation.
Education Secretary Michael Gove and Deputy Prime Minister Nick Clegg, who clashed openly earlier this year, will launch the reforms jointly after negotiating a plan agreeable to both sides of the coalition.
The changes, which apply only to England, are designed to introduce more academic rigour to exams for 15 and 16-year-olds amid concerns about falling standards and the dumbing down of GCSEs.
The deputy prime minister's aides have described the changes as "radical reform".
One teacher, clearly opposed to the scheme, tweeted:
The new plans will spell an end to modular and rolling assessments and a stronger emphasis on the more traditional exam at the end of two years of study. There will also be a limit to the proportion of top grades that are awarded after years of ever-rising numbers of As and A*s.
A row over the GCSE English results broke out last month after it emerged that grading boundaries for the subject were altered between January and June.
Angry headteachers claimed that exam boards raised grade boundaries in the subject halfway through the year amid fears that too many children were going to get a C.
Leaked letters show regulator Ofqual urged exam board Edexcel to change their boundaries amid concerns that there would be a rise in C grades. They called on them to act quickly to produce results that were closer to predictions for the subject.
Pupils have launched a petition to have their GCSE English Literature exam papers re-marked after they were left "devastated" by their grades, which they claim were affected by Ofqual's boundary changes.
Both Gove, the regulator and Ofqual have repeatedly denied that any political pressure was heaped on the boards to change grades.
Amid the tense atmosphere over this year's GCSE grading row and coalition tension after Mr Gove's plans for a return to an O-level-style exam system were leaked in June without the foreknowledge of either Cameron or Clegg, the "radical reforms" planned for the GCSE will divide teachers, pupils and politicians.
Two major changes have been made to the reforms after the Liberal Democrats made vociferous protests over the proposed changes.
Clegg has said there there will be no return to the two-tier system of qualifications that pre-dated GCSEs, when the academically talented took O-levels and the rest sat CSEs.
Additionally, the proposed implementation of the reforms has been pushed back until autumn 2015, after the next general election, meaning an incoming Labour government could potentially repeal the changes before they were implemented.
The Lib Dems responded furiously to the leak, the Deputy Prime Minister saying at the time he was against "anything that would lead to a two-tier system where children at quite a young age are somehow cast on a scrapheap".
It is understood that Gove and Clegg have worked closely together over the summer to find common ground. A source said it had been a "really good coalition process" and that the end result would "raise the bar without shutting the door".
Labour has not as yet indicated that it will oppose the plans, although it criticised the timing and the leaking of details to the press.
Stephen Twigg MP, Labour's Shadow Education Secretary, responding to the reports in the Mail on Sunday which leaked details of the reforms, said:
"It is inappropriate for an overhaul of GCSEs to be leaked while young people taking English GCSEs this year have been treated so unfairly, and are still in limbo.
"Politicians should not set an artificial limit on the number of top grades, rather the best work should be rewarded.
"New exams should ensure that young people are prepared for the world of work and the jobs of the future. However, it is not clear how this new system will ensure a breadth of knowledge and skills and that pupils continue studying English and Maths until age 18.
"There has been no consultation on these plans, rather they have been drawn up in secret and leaked to select media outlets.
"The Chairman of the Education Select Committee warned Michael Gove just a few days ago of his responsibilities in the ministerial code regarding leaks, which he seemed unaware of. And yet we have seen another leak of major education changes rather than them being presented to Parliament."