Bulging veins, a red face, clenched fists and saliva spitting from behind gritted teeth - anger is ugly. But it can creep up. You may be going along, perhaps becoming gradually more irate, but keeping your temper under control, when suddenly something or someone makes you explode. Uncontrolled anger may show itself for just a few seconds, but once it has appeared things will never be the same.

In most jobs losing your temper is unacceptable; in some, it may even mean the sack. But there are few occupations where someone can be sent to jail for it. Yet this is a very real threat for teachers. The example of Marjorie Evans, the headteacher who faced a three-month suspended sentence after being found guilty of slapping a boy in July this year, sent a shiver through the profession.

Many teachers know how close they have come to stepping over the line when it comes to disruptive children. Mrs Evans was eventually cleared of assault on appeal. But at her trial, the magistrate said the boy’s behaviour of kicking and head-butting Mrs Evans was not a mitigating circumstance. On appeal, Mr Justice McKinnon overturned the suspended jail sentence and branded the pupil who accused her a liar. But Mrs Evans came very close to having a criminal record.

In another case last year, newly qualified teacher Paul Everitt (not his real name) was sacked after he grabbed a pupil’s lapel to stop her leaving the classroom. The police were brought in to investigate. No charges were made, even though the pupils concerned and their parents called for prosecution.

So how are teachers prepared for the trials they face in the classroom? Newly qualified teachers and old hands alike reveal a worrying lack of instruction. “Courses tend to concentrate on the positive,” says Lottie Milne, a newly-qualified teacher in south London. Another NQT, Denise Wilson, is more damning. “You simply aren’t given any pointers with how to cope when you get angry. There is no anger management training at all,” she says. “Yet you can’t be put in front of 30 children and be expected not to lose your temper.”

A quick search in the library at the Institute of Education finds nothing under “anger management for teachers”, although The Chalkface Project is bringing out a publication with that title aimed at helping teachers cope with students’ anger. It seems teachers are expected to have no problem with anger.

“But we do,” says Ben Wye, a behaviour support teacher from Westminster. “It is a taboo subject but many teachers face it.” He quotes from Mick McManus’s Troublesome Behaviour in the Classroom, first published in the 1980s. “McManus reveals that in a survey, 75 per cent of teachers said they got angry and showed it,” he says. “Yet it isn’t talked about, not even in the staffroom. Teachers’ anger is completely ignored.”

Many teachers worry that to acknowledge an anger problem could lead others to question their suitability for the job, rather than offer help. So there are few solutions and little guidance, says Ben Wye. McManus’s book recognises the pressure on teachers, referring to stress as anger turned inward. Stress has become a key word for today’s teachers, an acceptable word for an unacceptable situation. Anger management remains taboo.

The pressures that cause stress to build up, and can lead some teachers to explode, are many. Pupils’ bad behaviour is one such pressure. A spokeswoman for the National Union of Teachers says its surveys of teachers show that aggressive language from pupils and a small minority of parents is increasing. “But the teachers can’t react, they have to be able to calm the situation,” she says.

Other pressures include growing class sizes and feelings of isolation - of being alone in front of the class. Denise Wilson says: “I love special needs co-ordinators being in the class because it can have a positive effect on the children and it helps me to keep control. You have someone on your side in the room with you.” The weight of such pressures can create a situation where one action can trigger a furious response. Common triggers include aggressive language, tutting, threatening behaviour, pupils not listening and talking out of turn. The irritation of having to repeat yourself again and again can quickly cause an already stressed teacher to boil over.

“I used to get so angry,” says Andrew Bryant, a London teacher who has now left the classroom. “I remember spitting with fury as I tried to get my words out. It was the gradual build-up of pressure. I knew once I had lost my temper I showed the kids I had lost control - and that is no good.”

He also says he had little support from his colleagues. “I remember going to the staffroom after one incident and saying how I had lost my temper with one particularly irritating pupil. Another teacher said that the girl never played up in her class. The implication was clear - it was my fault.”

Despite the dearth of advice on how to control your temper, there are recognised ways of dealing with it. But they need to be learned and practised.

“Control measures can consist of developing palliative skills and taking direct action,” says Ben Wye. Such skills include relaxing, exercising, meditating and refusing to dwell on the unpleasantries you face at school. “Don’t think about particularly troublesome children out of school or talk about them to your friends and family. Leave the problem in the classroom,” he says.

Direct action includes removing yourself from the situation before you explode, or telling the individuals you are getting close to boiling point and why. Denise Wilson has employed a tactic developed by educational consultant Jenny Mosley, pioneer of circle time. When she feels herself getting close to boiling point, she puts on a colourful hat.

“The children know this is a sign I am close to getting angry and I don’t need to shout any more,” says Denise Wilson. “They begin to police themselves, to get the others to settle down and avoid provoking me more.”

Lessening any stress generally may help. Careful planning of lessons and how to react in certain situations can make things flow more easily, while some teachers use breathing exercises, aromatherapy, or visualisation.

But anger, carefully used, can be a powerful weapon in the classroom. Threatening to lose your temper can intimidate unruly pupils into better behaviour.

“Sometimes pretending to lose your temper is a way of dealing with a class. It can shock them into more appropriate behaviour without you losing control,” says Ben Wye.

Control is the key. Anger may be a benefit to highlight the unacceptability of certain actions, but it must never take over. Losing your temper is unacceptable. Shouting through clenched teeth could simply reduce your credibility in the eyes of the pupils. To see your veins pulsate and spit dribble down your chin will do nothing but lessen any respect they may have had for you. Learning to control and channel the anger is essential for successful teaching. But if the anger does threaten to go beyond shouting, you know it’s time to leave the classroom.

Keep calm

* Think of traffic lights - red, stop; orange, think; green, decide what action to take

* Try to slow down your impulses

* Create a distance between yourself and whoever has made you angry. Walk to the other side of the room

* Avoid physical contact. Do not try to remove or touch the childadult, better to move away

* Say to the person: ‘I am angry because . . .’

* Have some recognised signal (such as a hat you put on) that indicates you are getting angry

* Plan in advance how you will deal with a disturbance

* Try to lessen your stress with breathing exercises

* Use palm massage

* Carry a sachet of lavender to inhale when feeling stressed

* Try giving up caffeine

* Visualise yourself when you are calm

* Remind yourself it will end

* Try to have ‘golden moments’ which give you a few minutes alone and at peace

* Avoid ruminating about an individual who has upset you. Don’t dwell on it.