Sir Ron Dearing’s greatest achievement is that something will actually happen as a result of his latest report. With a combination of conservatism and innovation, he has defied those who said that it would be impossible to change the 16-19 scene or to give a semblance of structure to the present rainbow of qualifications.

Considering the constraints imposed by his terms of reference, Sir Ron has done a remarkable job. The need to “maintain the rigour of GCE Advanced levels” and to “continue to build on the current development of GNVQs and NVQs” was hardly an auspicious start, and in the end led to some of the report’s contradictions. Although Sir Ron could not circumvent such a clear direction from the Government, his National Certificate at least points the way to a brighter future.

The other problem for the review team was the limitation to the 16-19 age range, when it was clear that a more holistic approach to post-14 qualifications was required. As the committee chaired by Professor John Howie found in Scotland, it was impossible to make sensible recommendations without commenting on pre-16 and post-19. Sir Ron has likewise stretched his remit; indeed, the entry level of the National Certificate is likely to prove one of his most useful recommendations. Awards below grade G in GCSE and foundation level GNVQ, which offer progression to foundation level, will contribute towards a National Award at entry level.

Together with the recommendation, endorsed by the Labour party, for school students post-14 to spend more time in the college or workplace, this will provide strong motivation for many who are currently disaffected. It will also give an impetus to greater co-operation between schools and colleges.

At the other end of the ability range, the inter-board S-level and the opportunity for school and college students to take modules of university courses are welcome, although the reaction of some universities, as reported last week in The Times Higher Education Supplement, failed to acknowledge the benefits of the early modules.

The best part of the report is the change in the AS examination, from an unpopular and difficult vertical half of A-level to a horizontal half, which will rapidly prove popular with those on A-level courses, young and old. Not only will the reformulated AS-level (to be renamed Advanced Subsidiary) provide an interim accreditation for those who do not wish to complete the full A-level course, it will also tempt adults on to A-level courses who might otherwise have been put off by the difficulty of the full course.

The new AS is likely to bring a welcome increase in breadth of study for many post-16 students. Four or five subjects over the two years will become commonplace, especially since the AS will still count for half the Universities and Colleges Admissions Service tariff points of an A-level for university entrance. The emphasis on key skills will add further breadth to the curriculum for all students.

Of all the attempts over the years to produce a National Diploma, Dearing’s family of National Certificates surely stands the best chance of success. Although the main qualifications on the certificate will come from separate routes, the inclusion of key skills brings a degree of unity. The concept of the four levels encourages both progression and familiarity with the certification process.

If this optimism proves to be justified, then the National Certificates will pass the main test of any over-arching qualification, as they come to be seen as greater than the sum of their parts. Only if that is the case, and also if (a big if) the gatekeepers to higher education and employment ask for them, will young people and their teachers regard the certificates as worthwhile aspirations.

The biggest disappointment in the report is that the three pathways - A-level, GNVQ and NVQ - remain separate, with little opportunity to move between them and no system of credit accumulation and transfer. The lack of credit transfer, in particular, is a major disadvantage.

There are some mixed messages concerning modular A-levels, and those who see the module as the essential building block of all parts of the post-16 system will be disappointed that its potential as an agent of credit transfer has not been realised.

The Gatsby Foundation project found little common ground between A-level syllabuses and GNVQ courses with similar titles. This means that existing syllabuses cannot offer students the chance of doing a common first year and then deciding which of the two routes to pursue in the second year. Two modules, at the most, will represent the common core of a Y-shaped course. If every subject title is assigned to one, and only one, of the separate routes, then even this will be impossible.

Nevertheless, as the School Curriculum and Assessment Authority and the National Council for Vocational Qualifications merge, and co-operation between examination boards and vocational awarding bodies increases, those who design syllabuses will create modules which serve more than one route and, in this way, credit transfer may grow from the bottom up.

For the time being, however, the bridging of the academic and vocational divide will come only for those students who study both A-levels and GNVQ courses. In this respect, the reformulated AS-level and the opportunity to take six-module and three-module GNVQ courses are very welcome.

The National Advanced Diploma, requiring qualifications in four distinct areas of study, as well as accreditation in key skills, is an irrelevance. Many students will have a range of studies, encompassing both breadth and depth, without the artificial breadth imposed by these four areas. Without a positive incentive in the shape of increased UCAS tariff points, very few students will choose this combination of subject.

The oddest section in the report concerns mathematics and science. This seems to have been included at a late stage, largely as a result of pressure from the university mathematics lobby. Sir Ron has attempted to solve two intractable problems: the declining proportion of students specialising in mathematics and science, and the perception that those who have passed A- level mathematics do not have as much mathematical knowledge as students in the past. The resulting recommendations include a GCSE paper in additional mathematics, more students taking further mathematics at A-level and a hint that the main A-level mathematics course should be made broader and harder. All of these recommendations will have the effect of reducing the number of students taking mathematics A-level.

The situation becomes even worse, because the section of the report on the comparability of A-level grades proposes that subjects which are below the average level of difficulty should be brought up to the average, but that subjects - which include mathematics and the physical sciences - which are more difficult than average should remain the same. This provides a further disincentive to students to take mathematics A-level.

Sir Ron was clearly persuaded of the good sense of making A-level grades comparable and it is therefore inconsistent to level some subjects up to the average, but not to level the hardest subjects down. In this illogicality lies the secret, both of the report’s success and of its failure. In the present political climate, the Dearing consensus solution can only be translated into action with the agreement of the political right, which has the ear of the prime minister.

Making any A-level subjects easier would be anathema to the right, as would the extension of modular assessment: the unification of the three pathways would be unthinkable, as would too much change in A-level. The failure of the report is that these obstacles could not be overcome, but that is hardly Sir Ron’s fault. His success is that he has brought reform and increased coherence by going as far as he can without crossing these forbidden waters.

John Dunford is president of the Secondary Heads Association and headteacher of Durham Johnston Comprehensive School