The number of state schools offering international GCSEs instead of the traditional exams has jumped by more than 300% in two years, according to new figures.
So-called IGCSEs in subjects such as English, history and biology are proving particularly popular with schools, according to data published by University of Cambridge International Examinations (CIE), which offers the qualifications.
In total, 400 state schools are now teaching IGCSEs compared to 97 in 2010 and 220 last year, the figures show.
Rising numbers of private schools are also using the exams - 500 this year, up from 302 two years ago and 350 in 2011.
Overall, UK schools made 50,000 IGCSE entries this year, the exam board said.
CIE said that the rise is down to the government's decision in June 2010 to open up and fund IGCSEs in the state sector.
The exams have long been favoured by many private schools, who argue that they are tougher than traditional GCSEs.
CIE said that they have seen a big increase in demand for subjects like English language and English literature, as well as history and biology.
This may be due to the government's introduction of the English Baccalaureate, which is awarded to pupils who gain at least a C at GCSE in English, maths, science, a foreign language and either history or geography, the board said.
IGCSEs in these subjects count towards the E Bacc.
Peter Monteath, UK schools manager for CIE, said that the "linear" structure of IGCSEs, which means pupils sit exams at the end, rather than throughout the course, is proving popular.
"The feedback we are getting from schools is that they like the flexibility of these syllabuses, which gives teachers more scope to explore different topics with students," he said.
"Their linear structure also gives students space and time to study topics in depth."
A Department for Education spokesman said: "Two years ago ministers lifted the ban that had prevented state schools from giving their pupils the chance to leave school with the same set of qualifications as their peers from the top private school pupils.
"It is excellent that hundreds of schools are now taking advantage of the freedoms given them."
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