When several dozen head teachers and other education worthies are summoned to Downing Street to hear the prime minister promise a "new era" for secondary schools, you can bet a general election is just around the corner.

Tony Blair at a green paper briefing for head teachers: Thoughts on other things?

It was a clever wheeze by the government. How much more impressive to have a Downing Street seminar, a Commons statement and an official "green paper" than a mere manifesto policy launch.

Yet, since none of the proposals will be put into effect until after the election, a manifesto launch is what it really amounted to.

Nevertheless, it was a fascinating document and one which may have set the agenda for the election debate.

Tony Blair clearly believes his focus on "education, education, education" at the last election was successful and he hopes to make schools - rather than the euro, to take an example not at all at random - the central debate in the forthcoming hustings.

Plenty of 'go' left

The plan to turn half of England's schools into specialist colleges captured most of the media attention but there is actually a lot more in the green paper, including big changes to the early years of secondary education and radical plans for private companies, businesses, churches and community groups to take on the running of schools.

All governments worry that the voters will think they have run out of steam. On education at least, no-one can now be left thinking the Downing Street policy "wonks" are in any need of Viagra. They are clearly still prolific.

There are also advantages to getting your policy statements out early: it can avoid embarrassments in mid-campaign. In 1987, the Conservatives suffered a serious election wobble when they launched their education proposals on the run.

Mrs Thatcher and her education secretary, Kenneth Baker, seemed to understand quite different things about the plans for grant-maintained schools.

Labour has also been extremely audacious in stealing yet more of the Tories' clothes. Their spokeswoman, Theresa May, seemed stunned and accused Labour of doing a "cut and paste" job on Tory education policies.

William Hague was prompted to write for the The Daily Telegraph suggesting the Conservatives would go further still and create new grammar schools.

Sneaky stuff

Specialist schools were, of course, a Conservative idea back in John Major's time. It is fascinating to see how the energetic Sir Cyril Taylor, of the Technology Colleges Trust, has moved smoothly from being an adviser on specialist schools to the Conservative government to fulfilling the same role for Mr Blair.

Labour has also rather sneakily taken much of the steam out of the Tories' "free schools" policy by offering successful schools the freedom to vary the national curriculum and teachers' pay and conditions.

However, while blurring the difference between Labour and Conservative education policies, the green paper did have the effect of putting some "clear blue water" between the government and the Liberal Democrats.

The latter have portrayed Labour's plans for specialist schools as the "death knell" for comprehensive education.

It is now hard to see Labour and Liberal Democrat candidates on the ground finding much to agree on in education.

As if to reinforce that, the Liberal Democrats also this week reaffirmed their commitment to reverse another Labour government policy, namely university tuition fees.

Pinching the Tories' clothes and upsetting the Liberal Democrats might be counted as a good day's electioneering by some in the Labour Party.

Alienated

There are others it may not be so wise to antagonise unnecessarily. Yet that is exactly what the Prime Minister's official spokesman did when he told lobby correspondents that "the day of the bog-standard comprehensive school is over".

Lord Hattersley: "Lack of understanding"

This prompted a flurry of complaints from the teacher unions and the head teacher associations who described it as "insulting" to those schools which have worked hard to raise standards over the past few decades.

It was a phrase - and the underlying attitude it revealed - which also upset traditional Labour supporters.

Lord Hattersley may have spoken for many in his party when he said it showed a lack of understanding of what went on in most comprehensive schools.

How it will play with the wider public - parents and voters - is harder to predict.

Solitary diversity?

One issue that may concern parents in rural areas is how the promised "diversity" can work when there is only one school within travelling distance.

What happens, for example, if your only local secondary school becomes, say, a languages specialist and your child has a natural bent for science or engineering?

The response of ministerial advisors is to point out that technology means schools can now offer distance learning and that pupils at one school can benefit from the expertise at another school hundreds of miles away. However that may not satisfy parents.

The green paper has, for the moment, taken the government's opponents by surprise, forcing them to reassess their own approach.

But secondary school issues have a way of becoming highly charged, as the grammar school row has proved for decades.

Labour has lit the blue touch-paper: Watch out for the electoral fireworks in the weeks and months ahead.