Those in favour believed content and grading were being diluted and were concerned about examiner quality and poor appeals systems. Opponents said exam fees would soar and teachers would be diverted away from summer-term teaching towards examining. They felt that independent schools would appear too detached and exclusive.

The idea gradually receded, but many of the supporters’ fears remain unaddressed. Too many syllabus rewrites seem to remove advanced material.

Many schools get 90-plus per cent of A or B grades at A-level. Top universities are overwhelmed with applicants predicted to achieve three As.

With younger age-groups, many independent schools never did key stage 1 or 3 tests. There was a 7 per cent drop last year in the number of schools in the Incorporated Association of Preparatory Schools taking KS2 tests, reflecting a belief that they are ill-suited to the breadth of the prep school curriculum. At KS4, Tomlinson’s flexible pathways have made little formal progress.

But it is at 16-plus that the parting of the ways seems potentially most dramatic. Specialised diplomas allow students taking vocational subjects to include some academic components, but in future it will be very hard for academic students to include vocational elements in their qualifications portfolio, thus forcing candidates to choose one route or the other. Most independent schools will opt for the more academic route.

A-levels were once the accepted academic assessment tool for 18-plus school-leavers. Most independent schools still do them, but the international baccalaureate (IB) has a growing band of supporters because of its perceived linear nature - in contrast to A-level modules - and compulsory breadth. The big question is: should we allow our 16-year-olds to choose their own course of sixth-form study or should we allow them to choose only within a single prescribed framework? The outgoing Prime Minister, who has promised an IB centre within every local authority, seems to believe in the former.

The choices increase with the emergent Pre-U, which promises significant linearity, greater depth and more differentiated grading. But will candidates be able to take the Pre-U in some subjects and A-level in others and still gain the full diploma? Which independent schools might be the first to jump to it remains to be seen. The selecting universities are still watchful, and employers may not welcome a proliferation of qualifications: it will not be easy to establish broad equivalences, as the heated debate about the new UCAS tariff for A-level and the IB shows.

In many ways it will be a pity if the independent and maintained sectors take entirely different academic paths: there is too little crossover between the sectors already. Harder, more open-ended questions and an A* grade at A-level may yet help to prevent such fragmentation. But for some independent schools such reforms may prove to be too little, too late.

Unless A-level reform is radical enough to satisfy the higher-flying academic schools, the imperative to say “we have waited long enough” may well become overwhelming - in which case the debate of 10 years ago will merely have changed its nature.

On all these issues, private schools are indeed independent. They make their own decisions, based on local circumstances and individual characteristics. They educate 7 per cent of the nation’s children, but they provide more than 20 per cent of its A-level candidates, so their custom represents big income to exam boards. Meanwhile, as a sector, we value choice and diversity: ideally, a small number of nationally approved qualifications to meet the full range of needs - academic, vocational and occupational - and available to schools and colleges in both the independent and maintained sectors.

Nigel Richardson is chairman of the Headmasters’ and Headmistresses’ Conference and head of the Perse school, Cambridge