Some of the country's most famous private schools are challenging exam boards to remark their pupils' GCSE papers after a sharp fall in top grades this year.
The OCR board is understood to be remarking English literature papers from high profile schools including Charterhouse, while the AQA board has received complaints from Haileybury, Uppingham and Rugby.
Teachers at the schools were concerned that their pupils may have fallen victim to rogue exam markers. The Times Educational Supplement reported that far fewer pupils at the schools had received A and A* grades in English literature this year than in previous years' GCSE results.
At Charterhouse, in Godalming, Surrey, 37% of pupils scored these top grades, compared to 69% last year, the supplement reported.
Matthew Armstrong, head of English at Charterhouse, told the paper: "It is simply unbelievable that a cohort with a very similar profile to last year's should have achieved such varying results."
At Haileybury, in Hertford, results were reported to have fallen from 49% of pupils getting A* or A grades last year to 30% this year.