Has a major education reform ever produced this degree of consensus? That must be the question, on the eve of the publication of Mike Tomlinson’s 200-page report on the future of secondary schooling.

With the ink just about dry on proposals for a new diploma system to replace GCSEs and A-levels within 10 years, the amount of goodwill, on the surface at least, towards yet another reform of England’s qualifications system is remarkable.

But will the changes succeed in their dauntingly ambitious aims, which range from reducing the country’s embarrassingly high post-16 drop-out rates to reversing years of rising examination demands on pupils and teachers?

Certainly, Mr Tomlinson, appointed as a conciliator with a brief to gain support from across the education landscape, must think the current position is just about as good as he could have hoped.

Both the main opposition parties are now solidly behind the changes, which will be formally proposed by an inquiry led by Mr Tomlinson, the former chief inspector, in 10 days’ time. Tim Collins, shadow education secretary, said last week that he expected that they would produce an exam “at least as credible as the existing A-level”, while the Liberal Democrats have also strongly backed the thrust of the plans.

University vice-chancellors have also come out enthusiastically in favour, while independent school headteachers’ leaders, another important constituency, appear at least to have been persuaded not to rubbish the plans.

Insiders pay tribute to Mr Tomlinson’s diplomatic skills. But two factors have helped him to sell the reforms to completely contrasting audiences.

First, few oppose his view that change is necessary to engage less academic youngsters. They need more options, particularly through the vocational route.

Second, many teachers are unhappy with A-level, the exam taken by more able pupils, because rising pass rates are making it hard for universities to choose between thousands of high-achievers. The report’s proposals, which will include the breaking up of the A-level A grade into three, a dissertation and the incorporation of advanced extension awards and a diploma, have pleased universities.

These changes seem sensible not only educationally, but politically, as a way of inoculating the plans against accusations that the system is being “dumbed down”.

As one member of the inquiry said: “Tomlinson has been able to keep both the traditionalists, who want academic stretch, and the progressives, who worry about the kids at the bottom of the pile, on side. It’s brilliant.”

Although the Government has hedged its bets formally on whether it will implement the report, ministers have become increasingly bullish. Charles Clarke, the Education Secretary, told the Labour conference that “we have to address this agenda”.

While it is impossible to say exactly how the reforms will be received - and one of the key factors will be getting people to understand their complexity - the early signs are good.

Last week, London’s Evening Standard, which was a staunch defender of the A-level “gold standard” as recently as a year ago, backed Tomlinson. Even the Daily Mail, though savaging the Government’s ability to carry through the plans, said they were not intrinsically flawed.

Preserving this hard-won peace between the various parties is going to be tricky, with one well-placed source drawing a somewhat alarming analogy:

“It’s like the early days of the Good Friday Agreement”.

The first job will be persuading the public that the reforms, though billed as radical, represent evolution rather than revolution.

It is impossible to write about the new diploma system without presenting it as a “replacement” for GCSEs and A-levels. But Mr Tomlinson has stressed that the new intermediate and advanced diplomas will centre on courses very much like those currently on offer. The new qualification will not mean the fragmentation of existing exams, he has said. Some GCSE courses, for example, could survive in their entirety rather than being broken down into modules, while the number of modules taken for A-level will actually reduce from six to four.

The design of the qualification will present further potential hurdles. For instance, one of the most radical elements is the requirement for all pupils to complete compulsory “core” subjects: functional maths, literacy and information technology, to qualify for an intermediate diploma.

This will become the benchmark school-leaving qualification. Mr Tomlinson’s report will not specify the detail of the core subject courses. But there is a tricky balancing act here. Currently, less than 50 per cent of youngsters achieve a C grade in English and maths GCSE. If the standard required in the core subjects were set at this level, the Government risks the charge that less academic pupils will be demotivated. Set the bar lower - and the indications are that the content of the core courses will be less than for GCSEs - and the “dumbing down” charge resurfaces. Thousands of pupils could end up with only very basic maths, for example, while for more academic youngsters the diploma itself could be devalued.

This touches on another central issue for the diploma: how to ensure that the qualification has value in its own right and to prevent employers and universities disregarding the overall award, looking only at pupils’

results in particular courses.

The Secondary Heads’ Association has said that the advanced diploma should be a university entry requirement. However, David Melville, vice-chancellor of the University of Kent, who sits on the group, said he did not think this was realistic.

Admissions tutors needed to be able to take a variety of factors into account when selecting students, including their backgrounds, so most would not support having the diploma as a compulsory requirement.

Teachers’ unions, who again, are cautiously backing the plans, will want to look at the detail of the proposals on teacher assessment, which will be greatly expanded, amid concerns that professional workloads could rise.

Funding is another huge issue. The review will not recommend an increase in the average amount of teaching time which will limit costs to an extent.

But its requirements are likely to run into a yearly figure of billions.

While it is impossible to predict spending decisions 10 years hence, Mr Tomlinson will have been heartened that all in government, including the Prime Minister and the Chancellor, appear committed to major reform.

The biggest hurdle, however, is timing. The group’s insistence on a very lengthy trialling period, with full implementation likely to take 10 years, has been welcomed almost across the board.

But it brings immediate and long-term problems. As one inquiry member said:

“Even if all the parties are backing Tomlinson at the moment, with the best will in the world, it may be difficult to keep party politics out of this major reform with an election coming up.”

We will certainly have a new prime minister, and may even have a different governing party, if and when the diploma proposals are realised. Whatever the reaction to this month’s report, that could still be a big “if”.

DIPLOMA TAILORED TO INDIVIDUAL GOALS

This month’s Tomlinson report will propose a four-level diploma qualification to replace GCSEs and A-levels by 2014.

It will embrace all current exams, including vocational qualifications and young apprenticeships.

The philosophy will be that every youngster should be able to choose courses tailored to their eventual goals, whether they are aiming at university or want to join the workforce at 18.

The new qualification will consist of compulsory “core” courses in functional maths, English and information technology, which every pupil will have to pass to at least intermediate level to gain the diploma.

Coursework will largely be scrapped to be replaced at advanced level by a cross-curricular research project.

There will be a big reduction in the amount of external assessment at all but advanced level, with many courses at intermediate level and below graded mainly using teacher assessment.