At Charterhouse, in Godalming, Surrey, which sits OCR's exams, 37 per cent of students achieved A* or A, compared to 69 per cent last year. Five of the six teachers who taught the GCSE this year also did so in 2005, and the 2006 cohort were high-flyers in other exams, achieving record results for the rest of their GCSEs.
Matthew Armstrong, the school's head of English, said: "It is simply unbelievable that a cohort with a very similar profile to last year's should have achieved such varying results."
The OCR A*A rate at Wellington, Somerset was halved from 55 per cent last year to 28 per cent. In the poetry and prose paper, grades fell from 59 per cent A*A last year to 19 per cent this year. The same students achieved 60 per cent A*A in their English GCSE.
Several schools which offer AQA's English literature exam are also unhappy.
At Haileybury, in Hertford, results fell from 49 per cent A*A last year to 30 per cent this summer. The board is switching to Edexcel's international GCSE as a result. The schools cannot find any common factor in their unusual results except a belief that rogue markers are not being supervised and corrected effectively.
There is also widespread unhappiness with the boards' stance over re-marking. Several schools said the boards were not willing to accept there might have been a mistake, even when presented with statistical evidence showing marks on one paper differ markedly from the others.
Mr Armstrong said of his experience with OCR: "Any sensible organisation would recognise the anomalies in our results and re-mark the scripts."
Justin Garrick, head of English at Wellington, said: "The thing that is most frustrating is that something is very clearly wrong, but there seems no way to get any redress."
David James, head of English at Haileybury, said: "I'm disappointed for the pupils. English marking is prone to some subjectivity. But this degree of inconsistency is extremely frustrating."
These schools, however, appear to have bucked the national trend. Across all secondaries, the proportion of A* or A grades rose from 18 to 19.6 per cent this year.
An OCR spokesman said it had found no evidence of any widespread problems with this year's exams. He said: "OCR carries out inquiries procedures and re-marks in accordance with the regulator's code of practice."
An AQA spokeswoman said that exam marking was thorough and rigorous, with examiners monitored throughout their marking. She added: "Everything is done to ensure we act in the best interests of all our candidates."