Geoff Lucas, the secretary of the Headmasters' and Headmistresses' Conference (HMC), which represents co-educational and boys' independent schools, and himself a former senior official of the Qualifications and Curriculum Authority, wrote that A-level no longer offers enough "stretch", especially for the most able students. Tinkering with "super-A grades", as the Government proposes, will not be enough to save it, Lucas declared.
So why is it that more independent schools, free as they are from any obligation to follow the national curriculum or government guidelines, have not signed up for the International Baccalaureate (IB) diploma, seen by many as offering both the academic demand and the breadth of study lacking in A-levels?
There are, in fact, more state than independent schools among the 70-odd English schools that have so far adopted the IB. Of the 500-plus UK independent schools with sixth forms, a mere 27 have so far taken the IB plunge.
Lucas believes there won't be many more. "Most of the schools who were committed to the IB idea have already gone for it. They were schools who had already done their feasibility studies before the A-level grading fiasco of 2002. There may be some others who are still looking at it as an escape route, but others have been put off, deciding that it is too costly or believing that there may be too much parental resistance to it," he says.
Why such a low take-up? One clue lies in the character of the 27 schools. They fall into three distinct groups. Eight are international or American schools, serving a largely cosmopolitan clientele in London and the Home Counties. Another eight are highly selective day schools, again heavily clustered in the London area.
The largest group - 11 schools - are boarding schools that have to look worldwide to fill their places. Recent evidence suggests that the long-standing international reputation of A-levels has been replaced, especially in Europe, by a demand for IB.
Jan Shilling, the head of ISCis International, is responsible for promoting Independent Schools Council schools overseas. She confirms: "We encounter an increasing number of internationally mobile parents for whom IB is a huge attraction. They know it is intellectually challenging; it allows them to keep their university choices open; and it offers an international currency which can easily be taken up around the world. Most German families, for example, are now much more likely to choose a British school that offers the IB."
Michael James, head of the co-educational Rydal Penrhos school in North Wales, admits that his decision to adopt the IB as an option from 2004 was partly determined by this change in international demand. "It has certainly boosted our recruitment, especially in Germany. The IB is only available in French, Spanish and English, and German families tend to prefer the English option."
However, James also suggests one possible reason for the sluggish take-up of the IB diploma. "At first, we had a real selling job to do with the parents of day pupils who needed to be reassured that, because students have to take twice as many subjects as at A-level, their children wouldn't have to do twice as much work.
"Local parents also needed reassurance that doing the IB would not handicap students in getting into the universities they wanted. We held an IB evening to which we invited a representative of Manchester University to assure them that universities do take the IB seriously."
But there are more fundamental objections to the IB programme that may ultimately limit the extent of its adoption. Many heads believe that, in achieving its renowned breadth, too much flexibility of choice has been sacrificed. To guard against overspecialisation, IB diploma students have to choose six subjects - three higher and three standard - from distinct groups. It is this prescriptive element that deters Graham Able, Master of Dulwich College. "Of course we want breadth in the sixth form, but the degree of prescription imposed by the IB does not suit all 16-year-olds," he says.
IB students cannot take all three sciences, which, says Able, constrains those who want to keep their options open between, say, medicine and engineering. He dislikes, too, the absence of any higher maths component in the IB which, in his view, handicaps potential applicants to maths courses at Oxbridge and Imperial College.
Like many heads, however, he finds much to admire in the IB and is enthusiastically incorporating some of its elements into Dulwich's sixth-form programme. The IB's compulsory extended essay, for example, has been cloned into a 3,000 word "research essay" that all sixth formers must complete at the end of their first year. And the theory of knowledge element of IB is replicated by encouraging boys to take the AS-level exam in critical thinking; at least half are now doing so.
A similar process of assimilation is taking place at Malvern Girls' College. The head, Pippa Leggate, knows all about the IB, having at one time been the IB Organisation's regional officer for Africa and the Middle East. She decided against its full-scale introduction but is incorporating many of its essential features: girls are encouraged to choose their A-level subjects as a coherent programme of study, and every girl is expected to participate in the school's "learning for life" programme, replicating many of the lateral thinking elements of the IB. "The programme is still evolving," she says, "but there is no doubt that it provides girls with a coherence that was lacking in A-levels only."
Imitation is the sincerest form of flattery. It is clear that many other schools are thinking along similar lines. It may be that, even if the IB diploma does not conquer the educational world, what will emerge will be a uniquely English version of it, preserving what remains of the strength of the A-level system and combining that with the breadth and creativity of the IB.