International Baccalaureate: If it's good enough for the Prime Minister...

If Tony Blair was a sixth-former today, he might well be studying for something other than those three A-levels that propelled him to Oxford.

Fettes College, the Prime Minister's Alma Mater, is the latest in a growing number of independent schools to embrace the International Baccalaureate (IB) - the multidisciplinary diploma that is fast becoming a favoured option for academically gifted students seeking to continue with a broader-based education than that traditionally offered after GCSE.

Some 42 schools in the independent sector now run the IB, though Fettes is one of just three doing so in Scotland, and the only one north of the border to still offer A-levels as an alternative. Demand for places is fierce, buoyed in part by the publicity surrounding Blair's recent conversion to the IB, which he has pledged to introduce in at least one state school in every local education authority area by 2010.

Key to the IB's appeal is its international credibility. It is taught in 124 countries, making it more transferable than the A-level when it comes to offering students the widest possible range of higher educat- ion options. Its other unique selling-point is its ecleticism: in-depth study in core disciplines is combined with a breadth of coverage of other, related subjects lacking from traditional sixth-form teaching.

Naturally, the ambitious nature of the IB programme makes it intensely demanding. Three "higher" and three "standard" elements, including English, a second language, an arts option and a science combine with community service and a seventh, compulsory, subject - theory of knowledge - to guarantee a packed timetable. In addition to obligatory end-of-course exams, each student must write a 4,000-word extended essay in a specialist area.

Recent converts say the IB's benefits far outweigh any downsides. John Fern, IB co-ordinator at Fettes, says the £5,000-a-term Edinburgh public school has been inundated with enquiries from far and wide since launching the diploma in September.

"I must have already met 40 to 50 sets of parents to talk about next year, as well as students from other schools who want to transfer here," he says. "The school is gaining a new boarding house for sixth-formers this autumn - a good thing because we're now looking to expand our numbers to meet demand for the IB."

Fern, an IB veteran from his time as head of history at Oakham School, Rutland, says it presents huge advantages for students keen to study at foreign universities. "The IB is recognised all over the world, but some countries have strict rules about which A-levels they do and don't accept," he says. "German universities don't generally accept business A-levels, but will accept economics. Japanese universities waive their entrance exams for IB candidates, but not for those with other qualifications."

Successful IB students are also benefiting from a growing appetite for the diploma among universities at home - thanks, in part, to ongoing controversy over A-level grade inflation and accusations of declining standards. Further kudos has resulted from the recent decision by Ucas, the higher education admissions body, to publish a new "tariff" equating the top IB mark with six-and-a-half A-levels at grade A.

Some head teachers have been so heartened by the IB's pulling power that they have scrapped A-levels. Katy Ricks, head of Sevenoaks School in Kent, which began phasing them out in 1999 and now boasts more than 400 IB students at any one time, says of the diploma: "Our students have considerable success in applying to university, with 90 per cent getting into their first choice institutions."

The IB also offers the added value, she argues, of using academic study to foster cross-cultural understanding - one of the founding principles of its Swiss-based validating body, the International Baccalaureate Organisation (IBO). "Feeling connected to the rest of the world has to be a good thing for a modern teenager," she says.

For a full list of independent schools offering IB diplomas, visit www.ibo.org