If you have been teaching since you were in your 20s, by the time you get to 59 you will have been in the profession for around 35 years. You will have spent around 25,000 hours teaching and perhaps half as much again on planning and preparation. You will have sat through hundreds of meetings, including at least 100 parents’ evenings, and spent around 6,000 lunchbreaks in the school canteen or the staffroom.

After all this, you would be entitled to think you deserved a break. Retirement might look increasingly appealing; the light at the end of a long, long tunnel.

But a surprising number of teachers are putting off their day of retirement and opting to continue working into their 60s. According to the latest Department for Education figures, 6,300 teachers are still working past 60. And of these, a large proportion - 79 per cent among secondary teachers aged 60-plus and 58 per cent among primary teachers - are not senior management, but still in the classroom.

Alan Byrne, who at 60 has been teaching for the past 40 years, has no plans to retire. For him, the key is in balancing the pressures of the job and avoiding burn-out.

“I work well under stress,” he says. “I’ve been off work five days in 40 years, and each of those days I was in hospital with a virus on my joints. I still come in at 7.30am in the morning. Last night, I left the school at 7pm as we had a volleyball festival, and I work every lunchtime. But it’s only stressful if you let it get to you.”

As the principal PE teacher at Stonelaw High School in Rutherglen, South Lanarkshire, where he has taught for the past 27 years, Mr Byrne has to practise what he preaches. A regular dose of exercise may be why he has managed to last the distance. But he acknowledges that the job has become more demanding. “There’s much more stress now,” he says. “Back then, it was all about the teaching. Now for PE, you have to do the same paperwork as the other teachers and then you have to take extra-curricular activities as well.”

Not all teachers share Mr Byrne’s desire to stay on, as shown by the reaction to proposals to raise the retirement age. Under plans set out by Lord Hutton last month, teachers will have to wait an extra five years to collect their pensions.

Instead of being eligible at 60, from 2015 teachers will have to wait until they are 65, rising to 66 from 2020.

The proposals have prompted teachers who are near retirement to look at whether they will be better off leaving before the changes come into effect. “Anyone within a sniff of a pension has said, `I’m getting my money before anyone else gets in and takes some of it’,” says one teacher on the TES online forums. He says the exodus is bad news for his school. “These older ones work unbelievable hours, being schooled in the goodwill values that existed before `outsourcing’ and `costing’ management speak,” he says. “They do the job so well it will be a tragedy to see them go.”

The prospect of a later retirement, coupled with the increased contributions towards their pensions that will be expected from teachers in the future, could prompt a stampede towards the exit. For those too far from retirement to take that action, their frustration is enhanced by being powerless to do anything about it.

At 46, Andrew Broadhurst, a physics teacher at Carre’s Grammar School in Lincolnshire, says he was already looking forward to retiring at 60. He is “furious” at the proposed rise in pension age. Aside from the financial implications, his main concern is working for an extra six years, or even longer: by the time he reaches 66 the pension age may well have increased even further.

“People burn out already - some of my colleagues have had to retire early on the grounds of ill health,” he says. “How can they expect anyone who is 65 to be able to teach a class of rowdy 14-year-olds? The stress that teachers face sometimes comes from the children, but it’s mainly from the sheer volume of things you have to do. You often put in a 50-hour week.”

But despite these pressures, those who opt to remain in the classroom when they could be cruising the Mediterranean are often motivated by a love of their subject and a passion for teaching. At 62, Noel Moran could be putting his feet up but instead is still teaching, as head of sixth-form chemistry at the Arnewood School in Hampshire.

“I just like teenagers - they’re nice people,” he says, with an almost apologetic smile. “The satisfying bit is when you can look into a student’s face and see the penny drop. I think that I’m doing my job if the children look forward to my classes and if by the end of a lesson they can understand something new.”

His love of teaching has perhaps been enhanced by his previous job, as a development chemist, a career that proved ultimately unrewarding. “When it got to the end of the working week, it was very difficult to feel that you had done anything that was all that important,” he says. Teaching, however, has proved very different. “When I started teaching chemistry, I sort of knew that it was the right thing for me,” he adds.

That is not to say it has been stress-free. He recalls disagreements with colleagues over pedagogy. “If people who are not scientists try to get you to work in a way that is born out of a combination of their desire to do what is politically correct coupled with their ignorance of the subject matter, that upsets me,” he says. “Sometimes, because of the nature of the scientific work I teach, I want children to discover the aim of the lesson for themselves.”

It was a combination of practical and professional reasons that made Iain Bruce decide to stay on at school. “My mortgage ran out when I was 61 so I had to keep going until at least then,” he says, laughing.

But that was clearly not the only reason. Three years after his mortgage was finally paid off, at the age of 64, Mr Bruce is still teaching Years 7, 10 and 11 at a north London secondary.

“It is a matter of loving teaching,” the head of English says. “The liveliness of the language makes teaching very satisfying. English seems to be one of those subjects where it’s more creative, and you get an imaginative response from pupils. It always seems to tap into young people’s imagination and ability.”

When he started out, Mr Bruce had ambitions for moving up the school. He has held some management positions, including key stage 3 co-ordinator, which was “less enjoyable”, he says carefully. But the classroom was his natural home. “I want to teach my subject. I’m a bit of a crusader for English,” he says.

For Mr Byrne too, it is a passion for his teaching that keeps him going. “I’ve thought about senior management umpteen times,” he says. “I would love the money, but basically I wouldn’t be doing what I love best, which is working with young kids. I also love seeing my subject develop and I enjoy being part of the kids’ improvement.”

After 30 - or even 40 - years in the job, teachers are able to keep going because they have learnt how to deal with the stresses and strains, and to ride the tide of constant change and new initiatives. In some cases, they might see policies go in and out of fashion, and come back in again. While the physical strains of teaching may be harder for an older person to manage, their hard-earned experience gives them an advantage in other areas.

One is knowing how to switch off when you are not at school, says Mr Bruce. “One of the curses of teaching is that you can never stop, but you learn to curb that as you get older,” he says. “You can’t re-use every newspaper article, magazine cutting or journal that you come across. You learn how to pace yourself. If you can do that, you don’t burn out.”

Older teachers also develop a different style of lesson that doesn’t need to be so taxing, says Mr Bruce. “My teaching now is not quite as frenetic,” he says. “When I started, I was terribly anxious about getting everything right. With experience, you know that you don’t have to tie every detail down. You can let pupils have some rein to expand and think for themselves.”

Despite the enthusiasm of these teachers, for many of their colleagues the idea of working past 60 is not exactly a cause for celebration. The reasons teachers have had a lower pension age than the bulk of the population - the workload, stress of the job and the demands of behaviour management - still remain.

More flexible ways of working, such as reducing teaching hours, are suggested in Lord Hutton’s report and could be a way of helping older teachers stay in the classroom. But for those teachers working at 60 and beyond, the fulfilment they get from their job coupled with the passion they still have for their subject are enough to offset the heavy workload and the pressure that it brings.

For Dr Moran, the realisation of how much he loves teaching - and how much it has taken over his life - was brought home when he attended a rehearsal at his local amateur dramatics society. “I took some books along to mark when I wouldn’t be doing anything, and I was struck, forcibly, that the room was full of adults who hadn’t brought their work with them,” he says thoughtfully. “They were leading normal lives.”

By choosing to continue past retirement age, his may be an abnormal life. But after decades in the job, it is difficult to imagine an alternative.

THE SECRET TO TEACHING PAST 60

1. Only keep teaching if you still enjoy it. “If you enjoy teaching, that reduces the stress,” says Noel Moran, 62.

2. Recognise if you are becoming overly stressed and learn how to manage it. “Teaching is a vocation and it’s only stressful if you let it get to you,” says Alan Byrne, 60.

3. Don’t be offended if people don’t always take your advice: “You end up not being precious about it,” says Dr Moran.

4. Build strong relationships with your colleagues - not only will it make your job more enjoyable, but you can share resources and cut down on the workload. “If material is shared, that takes the stress out of it,” says Iain Bruce, 64. “You’re drawing on a bank of experience and materials.”

5. Be open to new ideas, even if you do not always agree with them. “I’ve got young teachers in my department and I learn from them every day,” says Mr Byrne. “I encourage them to have their say.”

6. Nurture your interest in your subject and its development. “Nanoscience scarcely existed when I started out, and I now teach 15-year-olds material that was only taught at university,” says Dr Moran. “It makes the job more enjoyable.”

Original headline: Not the retiring type