This week's A-level results mark the biggest change to the structure of the "gold standard" since the debacle of 2002.
Back then, fears of a sudden rise in results prompted by the move to a modular ASA2 structure rather than improved standards, led to some apparently crude last-minute grading interventions.
Schools smelt a rat and the exams system was engulfed by a crisis that led to the sacking of Qualifications and Curriculum Authority chairman Sir William Stubbs and partly triggered the resignation of education secretary Estelle Morris. Thousands of papers were re-graded and a complete review of 14-19 education was set in train that led to today's Diplomas.
If anything, this year's A-level changes could be seen as bigger. Alongside a structural reform - a reduction from six to four modules - there is the new A* grade and the introduction of "extra stretch and challenge" for the most able.
Concerns have been raised about whether it is too much all at the same time. "The changes are placing a huge challenge on the system, there is no doubt about it," said one exam board insider.
So are we in for a repeat of 2002? Until yesterday's results are fully digested, it is impossible to say for sure. But it seems unlikely since that is exactly the scenario today's exam regulation system has been designed to avoid.
More formalised communication has been set up between regulator, Ofqual and the exam boards to prevent the confusion of 2002.
Just as importantly, historical statistical data is now an intrinsic part of setting grade boundaries, ensuring that standards can remain constant from year to year, even at times of great structural change.
Of course, that can create its own problems. As The TES revealed last week, exam boards have, in agreement with Ofqual, altered the value of some marks on some of this year's papers to ensure that the proportion of A* grades remains within expectations.
But The Headmasters' and Headmistresses' Conference was concerned that those expectations were based on last year's figures and did not take into account the extra pupil motivation sparked by the new grade.
John Dunford, Association of School and College Leaders general secretary, has been warning schools for three years about the extent of the 2010 reforms. "Anyone who thought this year's A-levels were like last year's will have received a shock," he said.
So another 2002 may be unlikely. But for a system where continuity and public confidence are so important, any change is potentially dangerous.