Eton and Winchester, as well as top day schools in the state and private sectors, entered candidates with the Oxford and Cambridge Schools Examination Board.
But according to the Government's examinations agency, the board's standards in last summer's A-level English were so lax that the markers relied on candidates' predicted grades rather than their examination answers. In one case, says the report from the School Curriculum and Assessment Authority, a candidate's score was raised from 14 out of 60 to 40 out of 60 "with no apparent justification".
The board failed to establish secure and appropriate standards and its procedures were described as "unworthy of a reputable examining board" by Dr Nicholas Tate, SCAA chief executive. It was not even clear if successful candidates had read the A-level set texts.
The OCSEB (now renamed the Oxford and Cambridge Examinations and Assessment Council) English examiners are in the middle of a long-running dispute about official changes in exam procedures. The former chief examiner in English, Dr John Saunders, attacked "SCAA stormtroopers" who wrote the report which he said is a deliberate diversion from the real issue.
He recently hit the headlines by claiming in The TES that thousands of talented candidates across the country could have been marked down by computer-standardised marking schemes.
The seven authors of the report on OCSEB's A-level English concluded that "it was not possible to have confidence in the validity and reliability of the examinations". Only five out of 5,341 candidates were failed by the OCSEB markers while nearly 30 per cent were given a grade A - against a national average of only 15 per cent.
The report was particularly critical of the "grade review meeting" held by the board which "lacked consistency, rigour and reliability".
"As a consequence," it continues, "many adjustments made at this stage were unjustified. The process of adjusting candidates' marks and grades without reference to the scripts, so that these were in line with centres' predictions, was unacceptable.
"In virtually all cases, changes of this kind were unjustified and unsupported by the work produced by candidates. There was no evidence to indicate the basis on which decisions had been made at the review meeting and it was evident that candidates were being treated inconsistently."
Dr Saunders this week accepted that there was an administrative breakdown last summer. He resigned at the time, saying he was unable to guarantee standards.
But he blamed SCAA for changing the national marking rules which meant that his team of markers had no statistical support. As a result, he said, his marking team chose to err on the generous side.