Manchester Grammar School is opting for the international version of GCSEs, which is in line with old-fashioned O-levels and allows pupils to dump coursework in favour of end-of-term examinations.
Its decision is opening the floodgates to scores of independent schools to do likewise in a range of GCSE subjects that could pave the way for the demise of the existing qualification.
Geoff Lucas, the secretary to the Headmasters' and Headmistresses' Conference (HMC), which represents public schools such as Eton and Harrow, estimated about 40 schools had either taken the decision to switch exams or were about to. Most were considering ditching maths because they believe the international exam is better preparation for A-levels. Some, however, are changing in other subjects as well, including English.
Most of the schools are considering the option in the wake of the refusal by the Education Secretary, Ruth Kelly to opt for the wholesale reform of GCSEs and A-levels recommended by the inquiry led by the former chief schools inspector, Sir Mike Tomlinson, into exams this year. Ms Kelly rejected his call for the exams to be replaced by an overarching diploma.
"Many schools saw that as a sign that not much was going to change with the examination system," Mr Lucas said. "The international exam includes more pure and applied maths, rather than the more consumer-led GCSE maths which can be about someone going down to the shops and buying 'x' amount of something."
Dr Christopher Ray, the high master of Manchester Grammar School, said: "It is easier to differentiate the brightest students. I would say most schools who are thinking about international GCSEs are prompted by a desire to do a coursework-free option.
"When you are dealing with able young men, you want something that will challenge them. The maths includes calculus, which the current GCSE doesn't, so it might be thought to be a little harder.It is clear that, while GCSE is appropriate for very many children, some GCSEs do not appear to be appropriate for the most able."
According to Cambridge International Exams, an offshoot of the Oxford and Cambridge and Royal Society of Arts exam board, there are 100 centres in the UK offering the international GCSE and 2,285 candidates taking it this year.
Leaders of the HMC and Girls' School Association, which represents independent girls' schools, are trying to persuade the Qualifications and Curriculum Authority (QCA), the Government's exams watchdog, to give it official recognition, which will enable state schools to offer it.
Without official recognition, the international exam results do not count towards national league tables and schools cannot get funding for pupils to take it.
QCA officials say they would need to be approached by the exam boards with a request for official recognition before they could grant it.