There have been numerous claims over the years that children work the system by getting parents to do their coursework for them.
And the advent of websites has made it even easier to cheat. As The TES reveals today, thousands of teenagers are signing up on-line to swap essays and practicals.
At least six major websites offer services targeted at British 14 to 18-year-olds and the Government and exam boards appear unable to take action against them.
Coursework.info, which boasts 47,000 users and is run by Student Media Services Ltd, describes itself as the "home of a collaborative project to preserve intellectual and academic information and catalogue it for the benefit of students".
Essaybank Ltd offers 3,394 GCSE, A-level and degree essays. Pupils pay pound;14.99 or submit an essay for a year's membership.
Courseworkbank.co.uk claims it is the UK's largest free coursework site, offering 2,260 GCSE, A-level and International Baccalaureate essays. It provides 118 GCSE and 29 A-level essays for free perusal.
Student Media Services also runs Writing Direct UK, offering tailor-made essays written by undergraduates. Rates are pound;167.95 for a 10-page A-level piece, or pound;95.95 for an eight-page GCSE essay, written at two days' notice.
A-level Coursework UK, run by a separate firm, claims to guarantee A and B grade A-level coursework, written to a student's specifications at pound;200 for a 2,000-word essay.
The websites deny that they are helping pupils to cheat. Charlie Delingpole, a director of Student Media Services, said: "You cannot simply cut-and-paste these essays into another document, because we format the data so that the essay is jumbled. We do not want to promote plagiarism.
"This information is supporting learning. Students do use these sites for revision. There's limited access to libraries and we are trying to provide a positive educational resource. We want to stop people using it in a bad way."
He also argued that the company must be respectable, as at least six schools include links to the site on their own websites.
A-level Coursework UK includes the warning: "Under no circumstances is our work to be distributed or passed off as your own."
Exam boards moderate, or externally check, a proportion of coursework.
Edexcel said it checked the first 10 pupils' assignments for each subject in a school, plus one in 10 thereafter.
However, the system depends to a great extent on teachers' honesty. One of the main safeguards is a statement that staff have to sign saying that the work is the student's own.
Yet exam reports last year said some were signing off work as authentic even when it was obvious there had been cheating.
No one is suggesting that most professionals are not honest. But in the hothouse atmosphere produced by the pressure on schools to improve results, and teachers overwhelmed with coursework during the spring term, there must be concerns that plagiarised work is slipping through the net.