The Qualifications and Curriculum Authority is to address teachers' concerns about mis-marking by launching an investigation.
Experienced teachers have been left dissatisfied with the way exam boards have handled their cases, and have not felt the regulator has helped the situation.
Eton College's dossier of bizarre grade patterns shows similarities to at least two others sent to The TES in recent years.
Just over a year ago, The TES reported that eight leading independent schools, including Eton, were in dispute with the AQA board over GCSE English literature. Several complained of strange grade patterns, which were out of kilter both with results in other parts of the exam and with the same pupils' GCSE English scores.
At Haileybury School in Hertford, 82 per cent of pupils had their marks improved when the school challenged their original marks.
Last September, Wootton Upper School, a Bedfordshire comprehensive, said it was considering abandoning A-level psychology after three years of marking disputes with the OCR board.
Wootton Upper's situation carried echoes of the English literature dispute and aspects of Eton's latest complaint. Its case appeared watertight: the Bedfordshire school could show that the grades pupils achieved on average in particular papers changed markedly from year to year. And yet, according to the school, the same teacher had taught each cohort for the three years in dispute and the pupil profile had not changed greatly.
The exam boards and the QCA tend to respond to general concerns about marking quality by pointing to the relatively small number of grades that are changed overall.
They also argue, rightly, that supervision of the marking process is usually painstaking, and that the move towards on-screen marking is likely to improve marking accuracy.
Against this have to be weighed claims that examiners do not always receive sufficient training. In 2005, The TES disclosed that a member of Edexcel's administrative staff was asked to mark religious studies GCSEs with 20 minutes' training.
Eton's latest file states that senior Edexcel music technology examiners left before the 2007 A-level. It also casts doubt on the experience of their successors.
At A-level, the statistics show that in 2006 only 5,778 grades out of 7,019,074 papers were changed after a re-mark or clerical check. This is fewer than one in 1,200.
However, schools and colleges challenge very few grades. In 2006, only 54,425 papers were queried, which is only around one in 130. Of those, 11 per cent resulted in a changed grade. Figures for 2007 will be published next week.
Teachers complain about the prohibitive cost of querying grades: a re-mark costs up to pound;38, and either the school or pupil pays unless the exam board admits a mistake.
Students who challenge a grade and find their marks reduced lose out. This means that only those confident that marking mistakes are in their favour will complain.
A 2004 academic study argued that exam results were only ever accurate to within one grade.
Against this background, the QCA's investigation, launched just as plans were announced to create a new, more independent regulator, must be welcomed. But what action will result remains unclear.
One teacher said: "I have dealt with the QCA before on grading issues and I'm not sure this will make any difference."
Eton's re-marking dossier:
- Two candidates in an A-level Russian paper got zero marks, but were later re-marked and given As.
- Between 2006 and 2007, GCSE English results swung from Eton's worst ever (30 per cent A-stars) to its best ever (71 per cent A-stars), without a significant change in either the pupil or teacher profile.
- A history student, who was graded U in one A-level paper, retook it and scored 120 out of 120.
- Some 25 GCSE design and technology coursework marks were reduced and the rank order of pupils' scores was changed after only 10 sets of work were taken in for moderation, but eventually all marks were reinstated.