When Reg Shore put his name forward to stand for Parliament, he knew he would have to develop an opinion on everything. One minute he might be asked about the war in Afghanistan, the next about the best place for a pedestrian crossing.

He hadn’t quite anticipated becoming an authority on letter boxes. But when you have spent many hours delivering thousands of leaflets, their design takes on an unexpected significance.

“There are three types of boxes,” he says. “The ones you just open and put the leaflet in - they are brilliant; the ones with a second flap where you have to put your hand in and push it through - they are fine unless there is a Rottweiler on the other side, which is more common than you would think. The third is the hairy kind. There is a flap, then a brush arrangement, then another flap - they are difficult. Worst of all is when they are at the bottom of the door and you have to bend down to shove this thing through. People who design these things have a lot to answer for.”

Exasperating they may be, but letter boxes have not yet dented Mr Shore’s dream of joining the ranks of teachers-turned-MPs. Teachers already make up one of the largest occupational groups among MPs (see panel overleaf). And this year’s election sees dozens more aiming to follow the same route from classroom to Commons.

Mr Shore knows this particular journey is unlikely to end in a place on those green benches. The head of the performance faculty at Trent Valley Academy in Gainsborough, Lincolnshire, he is Liberal Democrat candidate for Lincoln, a seat where his party came a distant third at the last election. “I’m aiming to pull some votes back and hopefully get into second position, if not first,” is his realistic ambition.

He has been a councillor, but getting on the list of approved candidates for a parliamentary election still meant a year-long vetting process. There were training courses on everything from policy details to dealing with the public, culminating in a day of interviews. A session in which people sat round a table having a go at him felt particularly close to home.

“I had to justify closing a school and one woman kept interjecting with screams of: `I don’t want my school to close’,” he says. “It was difficult.”

The next hurdle was to persuade a local party to adopt him as their prospective candidate. He was keen to stay local, so when the Lincoln Lib Dems were looking for a candidate, he applied and was selected.

But that was the easy part. Running an election campaign costs money, and without a local billionaire to bankroll him, he turned to duck races.

“We did one last year and that has been our main fund-raiser,” he says. “We need to raise enough money from the next duck race at Easter to run another leaflet for the campaign. It is hand-to-mouth stuff.”

He originally budgeted to spend pound;30,000 over two years. There was a quick recalculation when he found the local party had pound;200 in the coffers. He now reckons he will spend about pound;6,000 in total - “absolutely shoestring”, he reckons.

He has to raise the bulk of it himself, although a private donor did fund his first leaflet to the tune of about pound;1,600. “I try to go swimming, but when I can’t at least delivering leaflets is some kind of exercise. The dog gets a walk out of it, too,” he says.

As a council veteran - he is now on both the county and district councils - he is used to balancing his school and political lives. The school has arranged his timetable so he is usually free on Fridays and he leaves few minutes of the day unused. “It is about prioritising and juggling and coming in at 9pm and settling down on the settee with a beer,” he says.

The Lincoln constituency does not cover the school’s catchment area, so he reckons most of his pupils are unaware he is standing for election. Many of them know he is a councillor, though. “Some of them think I’m prime minister,” he adds.

Being a teacher has given him some advantages, which may help explain the profusion of teacher-MPs. As microcosms of society, working out where things are going wrong in school can translate to where things are going wrong in society, he says. He is also used to standing in front of an audience, fielding unpredictable questions. “The more you do it the easier it gets, and as you relax the teaching skills kick in,” he says.

Projecting your voice, using body language, the way you walk into a room, giving direct and personal answers to questions - tricks of the trade that have also helped Steve Mastin in his fledgling political career. A familiarity with public speaking stands you in good stead in an election campaign.

“When you have done an assembly for 300 people, public speaking doesn’t bother you,” he says. “Being a teacher helps enormously.”

Unlike Reg Shore, Mr Mastin has always had his sights set on Parliament. His plan was to spend 10 years teaching in the state sector before launching his political career. “I wanted to have done a real job first,” he says.

After a decade at Sawston Village College in Cambridgeshire, where he is head of history, he applied to go on his party’s list of approved candidates. After a gruelling process he was accepted and free to apply to constituency parties. Another series of interviews later he was chosen as the Conservative candidate for Redcar in the North East.

He is bullish about his chances, claiming his prospective constituents are the ones who have been most badly let down by the Government. Realistically, his chances of success are slim. The seat has returned a Labour MP at every election, and last time out the Tories came a distant third.

Funding is always going to be tight if you are a long-shot. Mr Mastin receives no financial support from the national party, so a lot of time goes into trying to raise cash to mount an effective campaign. No duck races for him though: fundraising dinners have been his major source of campaign finance. Even so he will have to fork out a considerable amount from his own pocket.

“I know I’ll go into debt because of this, but I went into it with my eyes open,” he says. “Having said that, it is only when you do it you realise what it involves.”

As well as leaflets and campaign literature, there are travelling costs and many incidental expenses: as the candidate, he is expected to buy lunch for campaign volunteers, for example.

Fighting a seat 200 miles from home presents logistical as well as financial challenges. During the week he works on the campaign “most days” after school, writing leaflets, composing letters to the local paper and organising events. At weekends he makes the 400-mile round trip, staying in a flat lent by a party member and spending the time canvassing, meeting voters and encouraging party members.

“Part of a candidate’s job is to inject morale into the local party and be the face of the party in the constituency,” he says.

Juggling being head of department with fighting an election is a delicate business. “I probably balance it very badly,” he says. He says his school has been supportive, seeing it as an alternative form of CPD, and he is discussing with his head the possibility of taking time off nearer the election.

“If I wanted to become a deputy head there would be courses I would go on. My career development is quirky but my head sees it as career progression,” he says.

Only six Conservatives MPs in the last Parliament were teachers, but Mr Mastin is happy to confound the stereotype of a left-wing member of the profession. He is also a member of the NUT executive in Cambridgeshire - “that gets tongues wagging” - although he is wary of bringing politics into school.

“I’m perfectly happy to talk politics but I don’t want to proselytise,” he says. “Pupils will know - they can do internet searches - but you have to be quite careful.”

Claudia Beamish decided not to campaign near her school until the election has been called. She did not want to be running into parents while out canvassing. This is her second time as a candidate, having previously stood for election to the Scottish Parliament.

“I’m quite clear about where the parameters lie,” she said. “I don’t think it is appropriate to be discussing my politics and asking for support from people I have a relationship with on a professional level.”

Ms Beamish teaches part-time at two schools, Abington and Braehead primaries. Abington falls inside the constituency where she is Labour candidate, Dumfriesshire, Clydesdale and Tweeddale in south west Scotland.

Hers has been an “incremental” campaign. Before December she was out twice a week delivering calling cards; now the canvassing is more regular and the constituency meetings more frequent.

Working part-time means she can set aside time during the week for campaign work. Monday is her Labour party day, while Friday afternoons are also free. But a quickening of the pace as the election nears has demanded more and more time.

“It has been a long haul,” she says. “Much as I love teaching, I feel it would be good to be doing politics all the time, rather than juggling the two. I don’t get much rest at the weekends, but I sleep well.”

The seat is the only Tory-held seat in Scotland, and Labour was fewer than 2,000 votes behind in 2005. But with Labour behind in the polls she knows she is an outside chance. “On a good day for Labour I think we will win,” she says.

As a primary teacher, the risk of pupils quizzing her on politics is remote, but working in small schools she is also keen to avoid talking politics with fellow teachers. There has been one potentially awkward staffroom encounter, however, when a colleague tried to pin her down on some aspect of policy. “I really had to be quite persistent in saying I don’t want to talk about that in school, but that is the only time it happened,” she says.

David Hallas did such a good job of keeping his political beliefs out of school that when he told his headteacher he was standing for election it came as something of a shock.

“He was quite taken aback,” Mr Hallas says. “I’ve been very keen to make sure that I’m politically neutral in school.”

Mr Hallas, a Year 6 teacher at Amherst School in Sevenoaks, Kent, was selected last autumn to represent the Liberal Democrats in nearby Tunbridge Wells. He was keen to avoid standing in a constituency that included the school’s catchment area, so he did not have to knock on parents’ doors.

Some of his pupils do know he is standing through seeing his name in the paper, although their reaction is not perhaps what he would wish for. “They said they hope I lose, so they don’t have to get another teacher in May.”

It would take a minor miracle for him to win: in the 2005 election the Lib Dems were almost 10,000 votes behind in Tunbridge Wells. Finances are tight and Mr Hallas relies on a small but dedicated band of volunteers to do most of the necessary legwork. “We try our best in terms of manpower but we don’t have the same financial resources,” he says.

Weekends are set aside for campaigning, and as the nights grow lighter evening work has been more practical. Easter is not so much a break as a chance to spend two full weeks on the campaign, and the school has agreed to release him for a week nearer the election.

But he is keen to emphasise that his pupils will not be missing out. “I’m a teacher first and the responsibility to my class is paramount,” he says. “Fortunately I’m a pretty well-organised person.”

Education plays a big part in his campaign: he stresses the Lib Dem commitment to cut class sizes for infant pupils to a maximum of 15, and the promise to give teachers more freedom.

“Teachers have been tied up in red-tape: we want to free up teachers, as long as they cover the basics,” he says. “Labour has put a lot of money into education, now we need to open up the curriculum.”

Matthew May put himself forward for election after losing the local council seat he had held for 12 years, a result that he admits was hard to take. He is now Labour candidate for the new seat of Northamptonshire South. His answer to the shortage of cash for his campaign is to turn to the internet. This also saves time knocking on doors.

“We have 55,000 voters and we need to reach all of them, and that is where social networking comes in,” he says. “It means we can get the word out without being on the doorstep so much.”

Making the best use of the limited time available to campaign is particularly helpful to Mr May, an assistant head responsible for Year 11 at Milton Keynes Academy. The election is expected to coincide with a busy time for his year group, who will be leaving school around polling day.

Fighting what he describes as the “17th most Conservative seat in the country”, based on previous voting patterns, gives him little prospect of success, but he has two objectives: to get into a position where he can contest a more winnable seat next time, and to leave the constituency party in better shape than he found it.

He has also found that experience in addressing large groups of people and fielding questions are not the only advantages bestowed by a teaching career. His background as a humanities teacher came in useful at one recent hustings.

“One of the first questions was about euthanasia and we had just started that topic in humanities,” he says. “It also meant I was able to show the pupils that this is an issue an ordinary member of the public was concerned about.”

Like all the teachers we interviewed, he says he wants to go into politics to “make a difference”, and this perhaps taps into one reason teachers are well represented among MPs. Just as their experience in addressing an audience may make them good candidates, so their sense of public duty makes them more likely to put themselves forward.

“I often find myself saying: `Why am I doing this?’, but I’m standing to try to do something about the society we live in,” says Reg Shore. “My greatest dream would be to win in May and be able to stop doing everything else. I would have so much time on my hands.”

An MP with time on his hands sounds like a recipe for trouble, but in the meantime those leaflets won’t deliver themselves.