There are now 69 independent schools in the UK offering the IB - an increase of 35 per cent on last year - and this figure is certain to rise still further come September. This mirrors a worldwide expansion of similar proportions. What's more, as the qualification becomes more widely understood, more schools are deciding to take the plunge and move towards ditching A-levels altogether in favour of an IB-only curriculum in the sixth form.
Among those whose classrooms will soon be A-level-free zones is King's College School (KCS) in Wimbledon, where day boys have been educated since 1897, when the school arrived on the site after moving from the centre of London. "I feel we've reached a moment in history," explains Graham Salt, the director of IB at the school, "where it no longer makes any sense for young people to reject influential ways of thinking while their minds are still developing."
This is a reference to the age-old Achilles' heel of the A-level system: the fact that it allows 16-year-olds to pursue a narrow selection of courses, thereby waving goodbye to subjects such as maths, languages or the arts - areas regarded in almost every other corner of the world as fundamental to an all-round education.
That may not have been such a crippling drawback in past decades, argues Salt, but it certainly is now, given the effects of globalisation and the onward march of technology. "Our pupils are likely to work in multinational environments, requiring a range of skills. In other words, they'll need to be intellectually flexible."
The persuasiveness of this argument was tested in September 2001 when KCS first introduced the option of following the IB route rather than A-levels. In just four years, the proportion of students opting for the new channel has risen to 50 per cent, with between 60 and 70 per cent expected to take up the IB this September. This has emboldened the school to announce that, from September 2007 onwards, there'll be no choice for sixth formers - it'll be the IB or nothing. The boys who started last September will be the first exclusively IB sixth form. The head, Tony Evans, a former chairman of the Headmasters' and Headmistresses' Conference, is a passionate advocate of the reform, both because of the breadth of study offered by the IB, and because of what he sees as the declining calibre of the A-level system. "The dilution of standards at A-level has accelerated since the 1990s," he maintains, "so much that the term gold standard is now a cruel chimera."
In contrast, the IB, he argues, is a demanding and comprehensive course that provides a perfect preparation for everything his boys will meet when they leave the school's red-brick solidity on the edge of Wimbledon Common. "We don't consider the IB a qualification for getting into university. We consider it a qualification for life," he says.
The IB system covers schooling from the age of three to 19, but it's the diploma level, for 16- to 19-year-olds, that's threatening to elbow A-levels aside in much of the independent sector. Six subjects are taken concurrently during the two sixth form years, three at higher level and three at standard level. Each student must include English, a foreign language, maths and one of the three main physical sciences in his six subjects. A fifth subject must come from the humanities family, and the final choice can be art, music, design or a second language, science or humanity. At the end of two years, students get a mark out of seven in each subject, based predominantly on performance in exams, but with an element of coursework as well.
In addition, pupils study a key component of the IB, called theory of knowledge, designed to stimulate critical reflection on the knowledge and experience gained inside and outside the classroom, for example by learning to recognise subjective bias, or to analyse evidence. They also have to produce a 4,000-word extended essay and participate in a creative, sporting or community service activity. In total, the maximum possible mark is 45, and universities making offers for places on degree courses will usually stipulate a minimum overall score, allied sometimes to one or two individual scores in the subjects to be studied.
Teachers firmly believe the breadth of experience can be a distinct advantage when sixth formers go for university interviews. They have more to talk about and more areas where they can demonstrate strengths. According to Evans and Salt, the two sets of boys who have so far left KCS with an IB, rather than A-levels, have certainly achieved at least as much as the other boys by way of university places, and arguably more.
Evans freely admits he had, and still has, an uphill struggle to convince parents of the benefits of the IB. "Parents here are naturally very conservative, having been reared on a concept of A-levels that is now totally outmoded." However, it seems that hearts and minds are being won around the dinner-party tables of south-west London, a shift of opinion propelled in part by the boys themselves.
The current crop of Upper Sixth formers say they received mixed messages when they were choosing between the IB and A-levels two years ago. In some parts of the press, the A-level system was taking a hammering, while elsewhere it was being said that universities didn't trust the IB. Among those who plumped for the IB, those doubts appear to have evaporated. "I don't regret it all," I was told by James Hawken, who's hoping to study medicine next year, having majored in biology, chemistry and English during his IB. Rob Hayward, who's aiming for a classics course at university, is also glad he made the decision to do IB. "It's been hard work, but the breadth of subjects gets you thinking about issues in the world. I don't think I'd have done that with A-levels."
And with testimonies like that from students heading off towards prestige university courses, it's hard to see how the IB can fail to gain more converts.