The credibility of the International Baccalaureate (IB) was badly undermined this week as it emerged that it has plagiarised large chunks of its marking guides from Wikipedia.
One of the confidential mark schemes, which provide examiners with model answers to help them grade papers, was for a history paper sat by around 20,000 candidates worldwide this May.
An IB examiner who spoke to The TES said they were "shocked" to discover there were "serious examples of academic dishonesty", throughout the document with guides for 14 of the 24 questions containing large sections copied wholesale from unattributed websites, including Wikipedia.
The TES has learned that the mark scheme is one of at least three being urgently investigated by the International Baccalaureate Organisation (IBO) over plagiarism allegations as part of a "wide review" into the issue.
The news follows last month's public naming and shaming of Jeffrey Beard, IBO director general, for plagiarising the work of another educationalist in a speech without acknowledging his source.
This week the IBO admitted that using Wikipedia, an online encyclopaedia that anyone can contribute to, was not "acceptable practice".
Wiki contributions "cannot be guaranteed because the sources are uncited", an IBO spokeswoman said.
She said a pupil who copied their exam answers or coursework from Wikipedia would be found guilty of malpractice and would not receive a grade.
The examiner who uncovered the marking guide plagiarism said they were "embarrassed" for the IBO.
"It will be difficult for me to insist that my students practice academic honesty when the very organisation which creates examinations and then assesses them according to often uncited materials does not follow these same guidelines," they said.
Another teacher who runs training workshops for the IBO said they were "livid" and "stunned" and that the whole IB programme had been put at risk.
Increasing numbers of schools in England have been turning to the IB as an alternative to A levels, with Michael Gove, education secretary, last month declaring himself an admirer of the qualification.
The American history paper with the most examples of plagiarism in its marking scheme was for the IB high level diploma.
It appears the examiners lifted uncited material, often copyrighted, from a variety of internet sources that also included websites like answers.com.
One guide to an answer took an academic's complete answer to a related but far from identical question straight from a magazine interview, without any acknowledgement of its source.
Geoff Lucas, secretary of the Headmasters' and Headmistresses' Conference, which has more than ten per cent of its member schools using the IB said: "One has to ask what the quality assurance system within the IBO is, to allow this to happen."
Mary Bousted, Association of Teachers and Lecturers general secretary, said it was an example of the risks schools could face if they moved away from England's well regulated exams system.
Jacqueline Harris, IBO assessment director said: "The IB treats all aspects of academic honesty very seriously. We have recently appointed a full-time manager with sole responsibility to review and promote academic honesty in all aspects of IB assessment. The academic honesty manager will be working with the whole IB community to this end."