On the night of last month's local government elections, John West spent more than £20 texting friends to let them know the result of the count for Aberdeen city council's Hazelhead ward. Not so remarkable for a politics-obsessed teenager, who, at the age of nine, pleaded to stay up late to watch the outcome of the 1997 general election. But West, 18, had a special reason to be in celebratory mood. A year after leaving school, and in the midst of revision for his first-year law exams at Aberdeen University, he was elected to the city council for the Scottish National party (SNP), becoming Scotland's youngest councillor in the process.

Not only that, his sister, Kirsty, 21, was elected in a neighbouring ward for the nationalists as well, as was 22-year-old politics graduate Callum McCaig. Twelve days later, as part of a coalition deal between the SNP and Liberal Democrats, all three were appointed to prestigious posts within the local authority. John West became Aberdeen's depute provost, the council's deputy civic head. His sister was named as education spokeswoman, and McCaig was appointed convener of the licensing committee.

The trio's emergence is precisely what Scottish ministers envisaged when they put in place a raft of measures to change the face of local government north of the border. Up until this year, Scotland's 1,200 councillors were predominantly male (79%), with an average age of 55. Only 1% were under the age of 30.

Keen to attract more women, young people and ethnic minorities, the Scottish executive lowered the age limit for council candidates from 21 to 18 and offered controversial golden handshakes to veteran councillors. The payoffs of up to £20,000 were part of a £7m package to persuade older and long-serving councillors - many of them Labour stalwarts in the central belt of Scotland - to retire. More than 400 took up the offer and stepped down. And, for the first time, the country's 32 local authorities were elected using the single transferable vote system of proportional representation.

Yet the success of the Wests and McCaig has caused some consternation. "I'm all for youth," says an Aberdeen taxi driver, negotiating the traffic on Union Street. "I've got children and grandchildren. But 18? Come on, what do you know at 18? I think you need someone with a bit of life experience."

John West, sitting in a borrowed office in the council's headquarters with his sister and McCaig, shakes his head at such sentiments. He says: "It has been said for years that the council is unrepresentative, that the council is a bunch of old men, and suddenly there's a lot of young people and now people are saying these people are too young to do the job. You can't have it both ways. Obviously, our role on the council is very important, but it's not like I'm an 18-year-old first minister."

Kirsty West nods in agreement. "We could be nurses caring for people, we could be doctors making life or death decisions," she points out. "People don't say: 'That nurse is too young. I don't want her caring for me.' What we are telling people is that you are welcome to disagree with our decisions, but you need to give us a chance. Don't write us off immediately. We are going to prove these people wrong."

It is the media, says McCaig, that has displayed the most prejudice. "I think it has been overhyped how much power we have been given," he says. "One newspaper had the headline: 'Here are the kids running your city.' We are just three out of 43. We are not running things. We have got the whole elected body of the council with us."

All three say they are still getting to grips with their new responsibilities and admit that they were a little taken aback at being asked to stand as councillors, and then to play such key roles within the authority. "I had never really had a career plan," says McCaig. "I had definitely thought about politics as a career, but I had thought about it further down the line. I thought you had to do something first, because when you are young, people are always looking for experience."

McCaig, a graduate of Edinburgh University, where he studied politics, comes from a family more politically aware than active. "There was always discussion about the issues of the day," he says. "I can remember a discussion about the poll tax when I was five, not having an idea what was being talked about but everyone getting quite passionate about it. When I grew up I learned to develop my own opinion.

"This time last year, I was graduating and was panicking looking for a job. I didn't know what I wanted to do. I was keen to get involved in the SNP. I wrote to a local MSP and said: 'Can I come in and help?' And then I was asked to stand for this."

The Wests are also the first in their family to get politically involved. "We didn't discuss current affairs as much," says Kirsty West. "We [were more into] historical things. We were members of the National Trust and we went to castles and stuff. We always heard all the history of it, the battles that took place there. That point of view is probably what got me interested in politics and interested in nationalism. My parents are both very keen on Scottish history, and my dad's pretty nationalist as well. I started getting into local politics. I was involved at branch and constituency level. I joined the party when I was 15."

She had been working for Aberdeen council as an administrator in the planning department when she was asked by the SNP group leader on the council, Kevin Stewart, to consider standing as a councillor.

Stewart also approached John West, who, like Kirsty, had joined the SNP when he was 15 and had helped out at the 2005 general election. He was in his first year studying law at Aberdeen University when he was asked to stand. After he was elected, his name was put forward for depute provost, a post that will require him to chair full council meetings in the absence of the lord provost, and to attend civic functions. He has been to two full council meetings already. His sister has overseen a recent education report.

Radical change

"These three, I would not have asked them to do these jobs if I didn't think they were capable," says Stewart, the council's deputy leader. "When I was first elected in 1999, I was the youngest on the council and I was 30 years old. I don't consider 30 that young. I think the council has to be representative of the community at large, and we still have a way to go in terms of women and people from ethnic minorities. I think that councils in some places required radical change."

And what a lot of the young councillors' detractors forget, adds Stewart, is that it was the voters who put them where they are. "The electorate wanted them," he says. "I think most people are excited by this situation."