Nine out of 10 of England's top independent schools have abandoned GCSEs in at least one subject for the more traditional international version of the exam.
A survey by the Headmasters' and Headmistresses' Conference suggests its members have switched rapidly to the international GCSE in English, maths and science, which they regard as closer to the old O-levels. The proportion offering at least one IGCSE soared from 57 per cent to 92 per cent last year. More than half the schools now offer the exam for maths, a fifth for science and 15 per cent for English.
The HMC includes some of the most academically focused fee-charging schools in the UK, such as Eton, Harrow and Winchester.
The IGCSEs, like their predecessor international O-levels, were developed so schools abroad could offer a British-style education without following the national curriculum. The Department for Children, Schools and Families and the Qualifications and Curriculum Authority refuse to recognise IGCSEs, meaning schools that use them suffer in national league tables. But that has not stopped dozens of private schools from making the switch.
Geoff Lucas, general secretary of the HMC, said: "This provides unequivocal evidence of the growing popularity and take-up of the IGCSE. The Government's and QCA's myopic policy of refusing to recognise it has done nothing to dampen independent schools' enthusiasm for it. This is a clear two fingers up to DCSF and a further nail in the coffin of league tables."
Independent schools opting for all pupils to take IGCSEs in English or maths will finish at the bottom of national league tables, on zero per cent. If many independents choose IGCSE, the effect could be to reduce the proportion of pupils gaining five or more GCSEs including English and maths, which will render the league tables increasingly unreliable.
The survey, answered by 101 schools, will be discussed at the annual conference of the HMC in Bournemouth next week.
Andrew Grant, head of St Albans School, adopted the IGCSE in English literature in his school last year. "There is deep disillusionment with the reliability of marking of GCSEs," he said. "Coursework has become a ritual which has to be got through. It is clear that schools are doing more than they should to get their pupils a good grade."
Far fewer schools are preparing to ditch A-levels: 12 per cent of respondents said they offered the international baccalaureate; just 8 per cent said they were likely to offer the Cambridge Pre-U, a more traditional version of A level.
Mr Grant said changes to A-level, including the introduction of A-star grades, made him confident that they would remain popular, while parents and universities might see the Pre-U as an untried qualification.