The top independent school in the West Midlands is to abandon some GCSE exams because they say they fail to challenge students.
King Edward VI High School for Girls took first place in the region, and fourth place nationally, in league tables for independent schools published today.
But the school, in Edgbaston, Birmingham, is to ditch the GCSE in mathematics, and may consider doing the same in science.
Pupils will instead study the international GCSE (iGCSE), a separate exam originally designed for British children living overseas.
Although it is accepted by all universities, the qualification is not recognised by the Government in official league tables. It means the school could slip back in official ratings.
But headteacher Sarah Evans said the traditional GCSE actually prevented teachers from stretching pupils.
"The iGCSE is much more exciting and stimulating.
"It does not include the coursework of GCSEs, which has become increasingly sterile."
Because coursework was such a large part of the qualification, teachers were forced to stick closely to the syllabus even if students were capable of more challenging work, she said.
The iGCSE also included more demanding topics, such as calculus and geometry.
"The exam boards have constructed the GCSE in such a way that it has lost its original purpose."
The school encouraged pupils to take further mathematics at A-level, which could lead to them studying the subject at university, she said.
"The country needs more maths graduates, but you have to get them hooked early.
"But it is very short-sighted of the Government to refuse to recognise the iGCSE in the league tables. In practice, it means state schools cannot offer it.
"Next year, none of our students will be taking the GCSE ? they will all be on the iGCSE. We may look at doing the same thing in subjects such as science."
Figures from the Independent Schools Council showed that more than six out of ten GCSE grades received by pupils at King Edward VI High School for Girls were A*. More than nine out of ten were A or A*.
The iGCSE was designed by education board Edexcel for schools following the British curriculum overseas. Despite the name, it is seen as having more in common with the old maths O-level than the GCSE.
King Edward VI High School for Girls is not the only domestic school to have adopted it.
St Paul's School in London, which yesterday took first place nationally in the GCSE rankings, has decided to ditch GCSE science in favour of the iGCSE, and could do the same for maths.
Jonathan Shephard, ISC general secretary, voiced concerns over the ability of GCSEs to stretch the brightest pupils.
"The GCSE is a valuable test for the broad range of pupils," he said.
"We do, however, continue to have concerns about the usefulness of some coursework and the GCSE's capacity to stretch pupils at all levels of ability.
"A greater and more immediate worry, though, is the increasing drift away from modern languages nationally.
"This is potentially damaging for the UK's future economic competitiveness."
A recent report by academics including Tony Gardiner, of Birmingham University, warned that Britain's economy was being held back by a shortage of maths graduates.
The issue will be taken up by Birmingham MP Gisela Stuart (Lab Edgbaston) when she meets Education Minister Lord Adonis next week.
Mrs Stuart said: "We know we need a more knowledge-based economy and to lead the way in science, but we will never achieve that if young people aren't learning maths."