As the exam board Edexcel admits to another mistake on an exam paper, BBC News Online looks at its history.
1996: Edexcel is formed by the merger of two exam boards.
22 March 2001: 10,000 sixth-formers are given the wrong results for an information technology exam (key skills test).
14 June 2001: Candidates sit a maths A-level paper which has been leaked, as shown on BBC News the night before.
August 2001: Bolton education authority complains 280 children have to wait for GCSE exam results.
4 October 2001: Chief executive of Edexcel, Dr Christina Townsend, resigns, saying it has been a "demanding year".
18 December 2001: It emerges that a question from a mock exam was in a paper taken during the summer.
18 January 2002: An AS-level maths paper with a mistake in it is taken by 2,500 pupils. Other errors emerge.
22 January 2002: General Secretary of the National Association of Head Teachers, David Hart, calls for Edexcel to be sacked.
The Association of Colleges complains of "widespread cocnern" among its members.
The Education Secretary, Estelle Morris, demands action.
1 February 2002: The exams watchdog, the Qualifications and Curriculum Authority (QCA), gives Edexcel a month to put its house in order.
The quango says Edexcel is "failing to meet its responsibilities to schools and colleges" and "too many of Edexcel's centres received poor service in 2001".
1 March 2002: QCA says it is happy with Edexcel's plans for reform.
20 April 2002: To tackle recruitment problems, the board plans to let trainee teachers act as examiners.
29 April 2002: Edexcel says candidates answered January's problematic maths question better than any other.
15 May 2002: QCA chairman, Sir William Stubbs, tells MPs all the big English exam boards - Edexcel, AQA and OCR - are struggling to find enough examiners.
Edexcel says missing or muddled pages in a Key Skills advanced level paper are an "operative error" at a printing company.
28 May 2002: Edexcel says an error in a government and politics AS-level paper was also due to printers failing to correct something.