Go for growth: The International Baccalaureate is still on an upward curve

The International Baccalaureate (IB) is booming in Britain. Latest figures show a 600 per cent rise in schools offering the diploma as an alternative to A-levels over the past 10 years, with a total of 210 UK schools now running it. That makes Britain the largest provider of the IB in the world per head of population.

Head teachers and students say this growth is driven by two trends: the educational merit of the IB programme itself, and a growing frustration with A-levels. "Schools have to struggle very hard to make the A-level system rich enough – the system doesn't encourage students to think for themselves," says Bernice McCabe, the headmistress of North London Collegiate School. "The IB offers students a much wider understanding of the world."

Last year, North London Collegiate obtained the highest average IB scores in the UK, and McCabe gushes about the programme. "There's just such an integrity to it. It combines speciality with breadth. You get the use of more open-ended and challenging questions that you don't get at A-level, the exam specification is less narrow, and it is less susceptible to political interference."

According to senior figures at the International Baccalaureate Organisation (IBO) in Geneva, the diploma's growth is expected to continue. Based on present rates and interest levels, their estimates suggest the number of UK schools offering the IB will double to 400 in the next three years. A significant proportion of this growth is likely to come from academies, nine of which have been authorised to offer the diploma in the past 18 months. High hopes are also placed on a potential Conservative administration extending this growth. A briefing note about the IB has already been sent to shadow ministers.

Students taking the IB diploma are encouraged to take six subjects instead of three, and their courses are assessed linearly rather than through modules. Pupils have to specialise in an extended essay on a particular subject, and do a broader course on the theory of knowledge. They also have to do 180 hours of creativity, action, service (CAS) over the two years – which can include anything from volunteering in Oxfam to playing basketball – to make up their final mark, which is given out of 45.

Emily Keen, 17, who is in the second year of the IB at Warminster School in Wiltshire says a lot of people tried to put her off studying for the IB. "They said it would be too hard and I wouldn't be able to keep up my extra-curricular activities," she says. "But actually, you have to do voluntary service as part of the course, so it was complementary." There's a perception that students who choose the IB think they're too good for A-levels, she says. "But that's unfair. The IB isn't more difficult – there's just a wider range of things to do for your qualification. You really have to enjoy learning to do the IB."

According to her head teacher, Martin Priestley, universities look favourably on the diploma. "If you slightly miss your A-level grades, then they [admissions tutors] will dig their heels in," he says. "IB grades are hard to achieve, but universities are prepared to show a degree of flexibility we don't see with A-levels. Past students keep saying they want to come back and explain what excellent preparation it gave them for university."

Given the IB's advantages – including the business case for providing a course that attracts international students – it's perhaps surprising that more schools haven't taken up the programme. Heads and teachers say they are obstructed by the costs of changing over – North London Collegiate had to acquire new teachers and buildings – and the fact that it takes two years or more to go through the authorisation process. "We need to see if we can improve our systems and make them less bureaucratic," says Adrian Kearney, the IBO's regional director for Africa, Europe and the Middle East."But we do need to make sure that every school is up to standard."

According to Priestley – whose school continues to offer students a choice between A-levels and the IB – the diploma will never completely replace A-levels, and that's a good thing. "Some people are hard-wired to be specialists," he says. "If you're a student who's crossing off the days until you can lose particular subjects, then the IB is not for you. But if a broad Western liberal education appeals to you, and you want to keep your options open, it has huge advantages."