Pop stars boast about it, comedians joke about it and tearful footballers even hold press conferences and own up to it. But for teachers the topic of illegal drug use is strictly off limits and a confession could cost you your job.

If staffroom chat ever turns to narcotics abuse, it’s more than likely that the latest government drugs education initiative or a wayward pupil is under discussion. But if teachers are anything like the population as a whole, quite a few of them know rather more about the subject than they would care to admit.

Research by the Institute for the Study of Drug Dependence shows that 40 per cent of people under the age of 40 have taken drugs and the Institute of Personnel and Development estimates that 18 per cent of the nation’s workforce are regular users. The Home Office estimates that 2 million people smoke cannabis regularly and another 5 million have tried it.

Ian Robinson, of the drugs advice charity Release, says: “We certainly know that, as with the population as a whole, teachers are using drugs. In fact, we had a call this morning from a teacher who had been cautioned for possession of cannabis and wanted to know if their school would be informed.”

There is nothing to stop the police telling a school of a teacher’s misdemeanour, but in practice it is unlikely to happen. Mr Robinson says that is the way it should be.

“I think we would all be unhappy if teachers were to use drugs in a public environment or in front of their pupils, but what they do in their own private lives is a different matter,” he says. “Drugs don’t necessarily affect your work, any more than alcohol or personal problems.”

Not everyone agrees and a growing number of employers, mostly in safety conscious businesses such as transport or the armed forces, have introduced checks. Some public schools have followed suit, but only test pupils suspected of using drugs.

Peter Smith, general secretary of the Association of Teachers and Lecturers, professes no strong views on the subject, but he is against extending such tests to teachers. “We would want to make a strict division between private conduct and the extent to which that impacts on performance,” he says.

Drug consumption in the profession is probably overestimated, he says. The ATL’s helpline has not registered one call from a teacher with a drug problem. “I can’t give you any evidence whatsoever that this is a problem. I have never known of a case in 25 years - even going back to the Swinging Sixties.”

But people in other high stress professions use drugs to wind down - a survey published by the Lancet claimed one third of junior doctors smoked cannabis - so it is not surprising to find some teachers who use it for that same purpose.

Paul, a humanities teacher at a secondary school in the Home Counties, has smoked cannabis on and off for 15 years, since he was introduced to it by a teacher who tutored him through his A-level retakes. He sees his habit as a form of therapy.

“Some people come home from work in the evening and have a glass of wine. I come home, put on some relaxing music and have a smoke. It’s a treat at the end of the day.

“When you first start teaching you can’t see the wood for the trees. You’re thrown in at the deep end and there is so much to take on board that I felt like I needed it.

“It became a bit of a ritual to come home from work and have a smoke. I found it enabled me to reflect on the day at a distance and work out how to deal with certain situations.”

But his drug use did have a downside - he began to forget pupils’ names and suffered from a sore throat. “It did get to be a bit of a problem in that way. But I actually think it was very beneficial in that I used to get ideas for things to do with the kids and I wouldn’t get so wound up.”

He keeps his habit a secret. “I don’t know of anyone else at my school that takes drugs. There are a few I suspect, but I would never talk to any of my colleagues about it.

“When you are teaching you have to be on the ball the whole day. There are not that many times when you can let up. A smoke helps you rise above the problems of the day.

“With the amount of work I have to take home at evenings and weekends, I think smoking helps me to switch off. If I feel like I have had a bit of a treat the night before, I go into class the next day feeling positive rather than resentful.

“I don’t think what I do is wrong because I regard it as quite therapeutic. Teaching puts quite a lot of stress on your mental health and well being. To me, smoking is a way of countering that.

“But as a teacher you are a kind of law enforcer and there is a kind of inconsistency in having that role and being a law breaker yourself.”

Anna, a former primary teacher in London, felt no guilt about her drug use, which she says was purely recreational. After working hard during the week she would let her hair down at the weekend on Ecstasy-fuelled all-night parties.

“I used to go to clubs at least once a month, more so in the school holidays, and take Ecstasy. I might also have a spliff (cannabis cigarette) or a bit of speed or cocaine.

“Friends got me interested in taking drugs. The first time was when I was a student and I had a half a tab of Ecstasy at a party. I didn’t dance or talk to anyone, I just sat there smiling for four hours. Whether it was the memory of it I don’t know but I felt really good for the rest of the week.

“It was never a conscious decision to regularly take drugs. I suppose it started with going out with my boyfriend and moving to London and going to clubs. It was all linked together - drugs, boyfriend and clubs.”

Anna says her drug use never interfered with her job.

“When I first started teaching I didn’t do drugs during term time because I was nervous and in a new job, so I wanted to be on my best behaviour and put my all into it. Then I realised I could do it and teach as well.

“I would feel a comedown usually on a Tuesday, but I would confine it to my personal life - usually by having an argument with my boyfriend - and it was quite short-lived.

“I would work 8am till 6pm at school, Monday to Friday, and I wouldn’t go out during the week. I would catch up on my work and sleep. Then come the weekend I would be well rested.”

She left her job after three years to have a baby. “I can only talk about it now that I don’t teach. I don’t think teachers ever admit to getting drunk the night before, never mind taking drugs.

“But I don’t feel guilty or hypocritical. I kept it quite separate from my teaching and I would never let it affect my performance.

“It isn’t a big deal. I even told my mum I have taken Ecstasy and cocaine. She’s quite a straight middle-class lady - it’s not as if she’s an old hippy - and she didn’t make a judgement. I think she just accepted that’s what young people do.”

Nowadays the only thing that keeps Anna up all night is her child. “I have grown out of taking drugs. But it’s something I look back on and I’m really glad I did it. It was great fun.

“I was young enough then and I could manage without so much sleep. But now I have got a child I don’t have the stamina.”

The names of the teachers have been changed