Keith Green isn’t rattled when a boy kicks a door or swears and hurls a book. He even kept his cool during a seven-mile march with a group of teenagers when one of them staged a sit-down protest and said he wasn’t budging. Nor does Green betray any emotion if one of his pupils elbows another in the face, starting a fight in the classroom.

A former soldier with the Royal Highland Fusiliers, he has dealt with far worse. Nine years in the army, including four tours of duty in Iraq, has effectively inured him to teenage tantrums.

“Iraq was extremely hot, extremely tough, extremely dangerous,” says Green, 32, who spent 11 months in Basra. “The riskiest incident was when we drove over a bomb and set it off. Everyone was safe but although we weren’t sure if we were a target or not we had to get our drills out under threat of attack and fix the vehicle.”

Living through such experiences, he thinks, gives former soldiers special skills when it comes to dealing with truculent teenagers. “Army instructors can be much more tolerant of bad behaviour than main-stream teachers,” he says. “And there’s a sense of humour that comes from being in the forces. It’s very rare that you’ll see one of us yell: ‘Get out of my class’.” Green, who leads a team of nine ex-servicemen and women working with teenagers in eight comprehensives in North Lanarkshire, is one of hundreds of former soldiers square bashing in schools – with remarkable results.

Under the scheme, launched eight years ago, former military staff spend one day a week for two years teaching children everything from first aid and team work to how to fill in a curriculum vitae or excel at sport. Since Skill Force started it has grown to 41 teams working with 9,000 children a year – as far afield as Bath, inner city London and the Scottish Highlands.

By the end of the courses the proportion of participants who are at risk of being expelled is cut from 36% to 6%, according to Jonny Gritt, the programme’s leader.

One of Gritt’s biggest success stories is Keri-Anne Payne, who won a silver medal at this year’s Olympics in Beijing. She has said that her life was transformed by the two-year programme. When she arrived in Britain from South Africa as a teenager Payne’s school suggested that she join the programme to help settle in. Although she was never badly behaved the programme gave her confidence during a time of upheaval.

The Tories are so impressed with Skill Force that they want to expand it fivefold, sending more ex-servicemen like Green into classrooms to become role models for bored, disaffected and shy children. “These men are heroes,” said Michael Gove, the shadow schools secretary, announcing the party’s plans this year.

So why does the scheme work? Green says that it’s all down to the military approach. “All the way through an army career you learn how to motivate people, which buttons to press to get the best out of them,” he says. “ The army philosophy is to look after your guys, the people in your charge. That instinct makes our instructors bond with the kids and gives them the feeling that we’re going to get through this together.

“We don’t take any lack of respect. We try to find out why a child is acting up and get him to understand the impact his action has on others. The military brings self-discipline – the best form of discipline – and that’s what we try to show them.”

The instructors delve into the backgrounds of their charges, says Green. “Children might be from a home where Mum doesn’t get up in the morning or make breakfast. We build up the picture.”

He is proud of the many success stories. “There was one kid who was very quiet in the classroom – yet when he went on a Duke of Edinburgh trip with us he came to life. It showed him what he was capable of, and he’s gone on to look at joining the marines.”

Another teenager, 16-year-old Peter Hamilton, a pupil at Graeme high school in Falkirk, is enthusiastic about the course – and says it has transformed him. “I was like a bad boy when I was 14 – backchatting teachers, not paying attention in class,” he says. “The course made me a better person.” Instead of abandoning his education at 16 he now has his sights set on going to college and embarking on a career in sports coaching.

“The instructors were much better at dealing with our class than ordinary teachers,” he says. “You could talk to them about anything.” He liked the way they rewarded good behaviour, giving points that could be collected and swapped for treats. “Ten points and you could go on a trip,” says Fraser. “It worked for me.”

Yet not everyone is happy with the arrival of soldiers in schools. Green says that when his team visits pupils’ homes to deliver awards or certificates, the reception is sometimes frosty.

“There is suspicion from some families, yes,” he admits. “It may be that one of their worries is that we might try to recruit their son into the army.”

Earlier this year the army came under attack from the National Union of Teachers, which accused it of targeting pupils in deprived areas. The union said it would back any teacher who boycotted armed forces material in schools, claiming it was based on “misleading propaganda”.

Green notes that many of the children in his charge come from coastal villages where career options are limited because of the decline in the deep-sea fishing industry, so a small number do join the forces. But more opt for what he calls “the uniformed services” – the police, the fire brigade and nursing.

“We don’t talk to the kids about the military,” says Green. “I think the army is a fantastic organisation, and I would never discourage them from joining up – but I am careful about what I say about it in the first place.”

Of course, for the servicemen, too, the move into schools reaps rewards. With a recession looming and 7,000 soldiers leaving the forces every year it can be tough to find jobs.

Gritt wants his instructors to be able to take a one-year teaching certificate course – a move supported by the Tories, who would give £9,000 bursaries to ex-servicemen who are graduates to train as teachers. They have also proposed the introduction of a British “GI bill”, which would pay for soldiers to take a degree after discharge.

“I do think it would be good if more people from the forces came into schools,” says Green. “Our instructors come from the same backgrounds as many of these children and speak the same language. Some teenagers can’t identify with teachers who are straight A-grade students and went from school straight to university. [Our] guys have been a success outside academia – they show the kids what can be achieved.”

Times recommends

• Students abandon the drink for gyms and juice
• Ofsted: third of Baby P-style reviews inadequate
• Top boys' school picks first woman head