But in a seat where the winner in 1992 had a majority of less than 900, politicians are perhaps more eager to make contact with school pupils, recognising that the 250 or so here are closely linked to around 500 people who are enfranchised. After all, advertisers long ago mastered the dastardly art of getting into parents’ pockets through their offspring.

School vice-captain Kevin Lang, an enthusiastic Liberal Democrat supporter whose scoop it was to persuade all four to participate, claims to have already converted his formerly Conservative-voting parents. Kevin, who at 17 is too young to vote, first noticed politics as a 10-year-old in 1990, during the protracted party leadership challenge to former prime minister Margaret Thatcher.

His perception of politics as exciting, unpredictable and monumental was strengthened by the result of the 1992 election. “Labour was hotly tipped to win and didn’t come anywhere near, ” he says. “It was such a big upset, politics got to me and I joined a party.”

Kevin was attracted to the Lib Dems because of the party’s democratic internal structure, and its advocacy of devolution and proportional representati on. “It’s the most honest party,” he claims. “It states clearly that there will have to be tax rises to pay for education and the NHS.”

The political affiliations of this sixth-year modern studies pupil, who hopes to make a career in politics, are not in evidence as he takes the stage to introduce the four candidates formally. Of the 250 fifth and sixth-formers present, only 19 will be entitled to vote for the party they wish to see governing Britain in the year 2000.

The hall in this 12th-century school (one of the oldest in Scotland) evokes the past and the future. Part of a modern building to which the school moved in 1968, it features stained glass and a pillared doorway (from the old school) which is opened only once a year for pupils taking formal departure from the school. The old Royal High School on Calton Hill will be the home of the Scottish Parliament if devolution goes ahead.

Former teacher and Scottish National Party MP Margo MacDonald, now working as a journalist, chairs the discussion and thanks the pupils for coming - “I do hope it was voluntary.” She introduces the candidates, who,with their super-groomed appearance and immaculate, oversized rosettes, sometimes seem to invite comparison with the line-up of finalists at a pony show.

SNP man Graham Sutherland launches the debate with an appeal for Scotland to become a “normal” nation, with independence, power over its wealth and a place in the United Nations. Calling for hard-headed patriotism, he says: “We don’t just want choruses of Flower of Scotland at Murrayfield and our Stone of Destiny returned. We want power over our destiny. Only with it will we have freedom.”

The loud and emotive use of the word freedom seems a deliberate evocation of a famous scene from the film Braveheart, which is alleged to have turned many eyes - young ones in particular - towards the SNP.

Liberal Democrat Donald Gorrie is more tempered in his opening address. But in an apparent side-swipe at Labour, he calls for “modest tax rises”. He says: “Improvements don’t just descend like manna from heaven”.

Of the Conservative Party, which defeated him narrowly in 1992, he adds: “Power corrupts, and a party that has been in power for 18 years cannot avoid that.”

Conservative Lord James Douglas-Hamilton, who has held the seat since 1974, says he is proud to be of service to his constituency and is learning something new each day. One of his most moving recent experiences,he says, was a visit to a museum dedicated to missionary David Livingstone,who had been brought up in a single room and had ventured into the wild with just his clothes, medical equipment and a Bible.

The achievements of Dr Livingstone demonstrate his “strong grounding in the Scottish education system”, says Lord James, to the relief of some pupils, who had been puzzling over the connection between Livingstone and this election hustings.

Highlighting jobs created in Scotland and his own strong support for the campaign Scotland Against Drugs, Lord James says his party stands for “a caring, strong, secure society”.

Former Labour group leader of Edinburgh District Council Lesley Hinds tells pupils that as a teacher, and a former pupil who was forced to move school because the building was falling down - she is keenly aware of the problems education faces. Ms Hinds reveals that Margaret Thatcher was responsible for her entry into politics. “I could see that the opportunities open to my generation were slipping away,” she says.

Pupils listen in respectful silence to the speeches. The politicians, who in surveys are down there beside journalists as the professionals held in most contempt by the public, are momentarily silent, perhaps because of the unexpected courtesy shown to them at a public meeting - no hecklers.

The schoolchildren seem a little inhibited by proximity to faces such as that of Ms MacDonald and Lord James, well kent from TV and newspapers. Perhaps, even though the kindly Old-Etonian aristocrat is a well-known figure in the school, the children feel distanced by his clipped accent and expressions, which call to mind the old Home Service presenters.

Perhaps the children feel estranged by the behaviour of the politicians here. The candidates play power games by writing their own notes or failing to look at rivals as they speak. This seems designed to give the impression that the speeches contain nothing of import. Not one candidate smiles at any point. Is this because Labour leader Tony Blair has been lampooned for his Cinema-scope grin? Are smiles trained out of candidates because they might be seen as a sign of weakness? Could it be that politicians simply have no sense of humour?

Perhaps pupils are dazzled by the brilliantly polished shoes under the table, which also seem standard candidate kit. Or maybe they are nonplussed by the passion of the SNP candidate and the controlled passion of the Lib Dem.

The pupils’ questions come now. “What will you do to relieve the pressure and stress on students, given that their average debt is well over #163;1,000 and many undergraduates hold down jobs to pay their way through college or university?”

“Should assisted places for intelligent children whose parents wish them to attend fee-paying schools help the minority at the expense of the majority?”

“One in 10 students has no job six months after graduating. How can you reassure pupils at this school who are about to embark on university courses that the future will be brighter for them?”

Pupils perk up when passion breaks out. Mr Gorrie decries the need for some students “to work for minimum wages late at night in pubs”. In response to the question about assisted places, Lesley Hinds storms: “If you wish to send your children to private schools you should pay for it, not other taxpayers.”

SNP man Mr Sutherland, a teacher at Boroughmuir High School, Edinburgh, furiously describes the scheme as a subsidy diverting money from books and teachers’ jobs in mainstream education. This government spends “only the equivalent of a fish supper per week per pupil”, he rails.

Lord James pours oil on stormy discourse. “I know it is tough for students but if you can see the course through, your earning capacity will be much greater.”

As well as being a modern studies teacher, Mr Sutherland has the advantage in communicating with the young people of never having been a councillor. He speaks like a normal person, using few of the politician’s stock expressions.

Pupil Anna Walsh - born a day too late to be able to vote on May 1 - says it is the SNP candidate who has impressed her most, but she would still have voted tactically for the Lib Dems, hoping to dispatch the Conservatives. Her vote is in line with a Scotland on Sunday survey this month of the views of Royal High fifth and sixth-formers on the constitution. More than 30 pupils desired the status quo, the stance of the Conservatives, but almost 60 wanted independen ce and more than 100 espoused devolution, the measure promoted by Labour and the Liberal Democrats.

Kevin Lang closes the debate with an appeal to his peers to use their vote. Perhaps he has in mind the pre-debate assertion by fellow sixth year modern studies pupil Samantha Paterson that many young people are contemptuous of politicians: “They think they’re a bunch of silly old men in suits taking money and having affairs. Nothing they do suprises you any more.”

* The other two candidates in Edinburgh West are Stephen Elphick of the Referendum Party and Gavin Corbett of the Greens