Politics isn’t supposed to be like this. Mhairi Black, a 20-year-old SNP activist from Glasgow, is standing against Paisley and Renfrewshire South MP Douglas Alexander, shadow foreign secretary and Labour’s chair of general election strategy, who commands a majority of nearly 17,000.

Black should have been chapping on doors for a lost cause, consoling herself that at least she was racking up campaign experience. But on 4 February, pollster Lord Ashcroft blew that theory apart: Black is on course to win the seat, he predicted. If she pulls it off, she will be the youngest MP to sit in Westminster for more than a century, and the youngest ever woman.

It started with a teacher. Black came from a political family where the news was always on television, CND marches took the place of weekend strolls and lazy thinking was challenged around the dinner table. But school provided the catalyst that propelled her towards politics.

Mr McMenamin taught Black modern studies at Lourdes Secondary School. She was not short of indignation at injustices in the world - feeling the closure of Clydebank shipyards particularly keenly, as much of her family hails from the town - but her teacher taught her that opinions were not enough.

“He would say, `Well, what are you going to do about it?’,” she recalls. “Every time that would knock me right back.I’d be on the bus home thinking, `How can I do something?’ ”

Painful rites of passage

For Black, a University of Glasgow politics and public policy student, the answer was to join the SNP, although she didn’t consider a political career until very recently.

“I always got the impression that politics was almost reserved for a few destined people, and the rest of us just had to look in on it,” she says. “Mods [modern studies] showed me that, no, it shouldn’t be like that - that if you’ve got something to bring to the table, you should do it.”

Old schoolfriends have been supportive - “Good on ye, go and get them telt!” said one she bumped into recently. But Black has already suffered one of the painful rites of passage of a political career: a tabloid shaming, after a newspaper pounced on unguarded tweets she posted when she was younger. But she plays down the experience as “part of the game” of politics and says that nothing should dissuade young people from putting ideas forward.

“School’s the one place where every wean gets a chance,” Black adds. “It’s about taking ordinary kids and showing them they’re just as good as anybody else.”

In 2010 the SNP and Labour were almost neck and neck behind the Liberal Democrats in the Aberdeenshire seat of Gordon. With popular MP Malcolm Bruce stepping down this year, and the Lib Dems polling poorly, a chance has arisen to capture the seat.

The SNP has turned to one of the biggest beasts in politics: its former leader Alex Salmond. Meanwhile, Labour has chosen Braden Davy, a 23-year-old who was previously serving up burgers in McDonald’s.

Davy grew up in the North East of England and a pivotal moment came when, aged 15, he joined the Northumberland Youth Cabinet, gaining responsibility for allocating pound;20,000 to school projects. The best way to spark an interest in politics is through projects such as this where pupils have genuine influence, he says, adding: “If it is tokenistic it’s self- defeating - if young people are keen to get involved, then find out they can’t do anything worthwhile, you knock that confidence.”

Davy lived in the mining town of Ashington but “I didn’t realise I was from a poor background until other people told me I was”. A “student voice department” at King Edward VI School in Morpeth gave him a broader perspective - the drop-in service included several student-led clubs and the chance to join programmes as far afield as China.

He became frustrated by a dearth of prospects for school-leavers in the area and the centralisation of power in London, so attempted to a start a political party that would secure more influence for Northumbria.

Now, as a Labour candidate, he reports a good reception from other young people who appreciate his experience of issues such as zero-hours contracts and sky-high housing costs.

“What better way to get young people interested in politics than getting a young person into Parliament?” he says.

Another candidate, Ross Greer, must be one of the most politically experienced 20-year-olds around. He joined the Scottish Green Party aged 15, and by 2013 was communities coordinator for the Yes campaign in the independence referendum. Since then his party’s membership has surged from 1,700 to 8,500, up to 40 per cent of whom are under 30 - thought to be a far higher proportion than in any other party. Greer is standing in East Dunbartonshire against Liberal Democrat Jo Swinson, herself the UK’s youngest MP between 2005 and 2009.

Eco-schools work during his time at Bearsden Academy grabbed his attention, but a bigger influence was religious education teacher Bill Storrie. “He taught me to question everything in the world around me and some very, very valuable lessons about critical thinking,” Greer says. “A good teacher’s job should be to never stop playing devil’s advocate.”

Avoiding controversy `fails’ pupils

The biggest gap in the Scottish curriculum is a mandatory political education, Greer argues, adding that young people have no shortage of views but “fear the unknown” and need to be shown how to register to vote and what to do in a polling booth.

Local authorities are “absolutely terrified” of letting young people explore serious political issues for fear of appearing biased, he says. “I find again and again that teachers are actively discouraged from engaging students in politics.which is a complete failure to prepare young people to be an active part of society.”

It is “absolutely essential” to have young candidates as they can speak up on issues such as tuition fees, benefits and college places, Greer insists.

“Young people just don’t engage with politics if it looks like something they’re not supposed to engage in for another 30 or 40 years,” he adds. “If they aren’t at the forefront of politics, fighting for what’s in their best interests, then there is a risk that no one will be.”

Disappointment with some aspects of school drew 19-year-old Taylor Muir to the Conservatives, for whom he will contest Rutherglen and Hamilton West.

He took modern studies at Rutherglen’s Stonelaw High School but found the subject lacking. Sections on UK politics focused too much on voting systems rather than ideas, with the result that pupils became far more interested in countries such as the US and South Africa.

“You could have got an A just by knowing how `first past the post’ works.You didn’t really need to understand politics,” he says. “The problem is that teachers have to teach towards the exam.”

Muir comes from a Labour-voting family, but favours an education system where teachers have more freedom to tailor approaches to individual pupils (he believes many pupils’ aspirations are not raised high enough in school) and decided that only the Conservatives had the radical ambition to achieve that.

Schools have to show how political activism can make a difference, he says, citing the famous 2005 case of girls at Glasgow’s Drumchapel High School campaigning on behalf of asylum-seeking schoolfriends under threat of deportation.

Muir combines activism with second-year law studies at the University of Strathclyde - he may have an exam on polling day - and 16 hours’ work each week in a call centre. Yet on the campaign trail his credentials are frequently questioned because of his youth.

“That’s the most depressing thing to hear,” he says. “If that is the attitude given to young candidates, then it’s just going to put young people off politics even more.”

How the human factor can promote political literacy

Modern studies has a strong tradition in Dundee, where Dave Keenan is principal teacher of the subject at St John’s RC High School.

In the first three years of secondary, St John’s builds political literacy in a subtle way, with no overt teaching on structures and systems such as how proportional representation works or what an MSP does.

“Instead, we often get pupils interested by seeing how people are affected,” Keenan says. “How does poverty or crime affect people in Scotland, for example - we can get the political stuff in that way.”

In a particularly successful task, S3s create television adverts for mock US elections. After this, “each one could tell you the difference between a Liberal and Conservative.about turnout and voter apathy”, Keenan says.

This helps to make sense of Scottish and UK politics, too, and pupils go on to investigate topics of their choice, such as how the government tackles terrorism or football hooliganism.

The independence referendum had a big impact and Keenan saw “all kinds of kids” discussing it in every corner of St John’s.

“Some of the best contributions I heard in the whole referendum build-up came from young people still at school,” he says.