GCSE coursework has become "less valid" and should be scrapped in several subjects, the exams watchdog has said.
Far less work will be done at home in future
A Qualifications and Curriculum Authority (QCA) report says coursework "does not fulfil its stated purpose" in an age of league tables and targets.
Amid concerns about cheating, it was announced last week that maths coursework will be scrapped next year.
It should also end in subjects such as English literature and the humanities, or be more controlled, the QCA says.
If it is retained, it will be done under supervised conditions and be set and/or marked by the exam boards - not teachers.
In areas which most obviously require practical assessments - art, design and technology, home economics, music and PE - it will continue but with "stronger safeguards".
Most changes will affect courses starting in 2009, following consultation.
Science has been left out because GCSE courses changed only last month. They involve 25% coursework, much of it already classroom-based.
Decisions on English language and ICT will follow changes to incorporate "functional skills".
The lead has been taken by the English regulator, but working closely with its counterparts in Wales and Northern Ireland. The changes will apply across the board.
Maths was singled out because of the "striking" responses to a survey of teachers.
"In contrast with all other subjects, a substantial majority of mathematics teachers (66%) disagreed with the proposition that coursework was valid and reliable," the QCA said.
They also had the highest levels of concern about different aspects of coursework, "such as authenticating candidates' work".
In other subjects the responses were "fairly positive".
There were concerns about the workload faced by both students and staff, but most teachers "are not overwhelmingly worried about the use of the internet for coursework".
Most teachers wanted some coursework retained.
But the QCA says things have changed since coursework began almost 20 years ago, with achievement and attainment tables, national or local targets based on exam grades and links between teachers' pay and students' results.
"The environment now is far more pressured and in these circumstances, it is likely that internal assessment of GCSE and A-levels as presently practised has become a less valid form of assessment."
It was seeking the most valid and reliable form of assessment for the intended learning outcomes.
But it also had to consider "manageability" - moving entirely to external exams would be far more costly and require the recruitment of many more examiners each year.
In spite of the report's contents, the QCA's chief executive, Ken Boston, said the current system of GCSE examinations and coursework was "robust".
"We are confident that the changes we are making to coursework will ensure that the GCSE remains fit for purpose, and ultimately reduces the assessment burden on both students and teachers," he said.
Education Secretary Alan Johnson received the QCA's report in June, and outlined the changes at the Labour Party conference last week.
He said: "Despite our rigorous system, more needs to be done to assure all parents that coursework assesses pupils' work in a fair and robust way."
But the National Union of Teachers accused the QCA of being "draconian".
Its head of education, John Bangs, had concerns about the proposed alternative, controlled assessment.
"We don't know what it looks like. So you've got rid of something before you know what is going to replace it."
The head of the NASUWT union, Chris Keates, was suspicious about the "sudden obsession" with cheating, coinciding with the greater use of the internet.
"Children from advantaged backgrounds have always had access to resources and opportunities to support coursework research denied to disadvantaged children," she said.
"Now access to a wide range of information is available to more children, concerns are raised about cheating."