There are two options if you want to shed the cares of the classroom along with gravity - retrain as an astronaut or get into a flotation tank. The second option is cheaper and more pleasant. And you don’t have to wear moon boots.

As you lie in the dark in a warm Epsom salt solution, your muscles relax, your vertebrae slip into the alignment that’s apparently necessary for perfect posture - and your brain, unless you’re someone too serene to need stress relief, carries on worrying. Many first-time floaters worry about lying in a box with the lid shut, long after they have been told that it’s a big box and that you can have the light on and the lid open - although this will make the tank lose heat and it’s more restful in the dark.

Once the soothing music has faded out and you are floating in silence, there is endless potential for worry. Are your earplugs in properly? (They are. ) Will you drown? (You can’t.) That’s before you even start worrying about work, money, the sick cat and all the things that led you to peel off all your clothes, get into a box full of water and pretend you’re in the Dead Sea.

“This will pass,” intones the mega-calm Tim Strudwick of Floatworks, a floatation tank centre in a converted warehouse on the Thames near London Bridge. “The mind takes longer to adjust than the body.”

On the first session everyone finds thoughts keep coming into their heads, says Tim reassuringly. “It helps to concentrate on your breathing. It does gets easier every time.”

Tim, who used to work in a City dealing room, discovered floating when he slipped a disc six years ago - it often helps with back pain because it takes pressure off the spine. With his Floatworks partner, former fitness instructor Pete Marsh, he restores equilibrium to many stressed-out former colleagues - and a fair number of teachers.

Sheila Mountain, special educational needs co-ordinator at Cranmer middle school in Mitcham, Surrey, seemed in need of a tank when term ended with a blitz on paperwork. Cranmer is in the midst of some of the biggest council estates in outer London and has 120 pupils with special needs - a quarter of its intake.

Sheila has been teaching for 22 years but was new to the special needs post when the code of practice was introduced in 1994. “Like many SENCOS I came in at the deep end, having to get the policy in place,” she says.

Although most co-ordinators approve of the code in principle, many feel the job has become more stressful since its inception. “The paperwork is very onerous and there is never the time you need to liaise with colleagues, ” she says. “I know several SENCOs who have taken early retirement - my husband is one of them.”

A National Union of Teachers study reported last month that SENCOs in primary schools had as little as two minutes a week to spend on each pupil with special needs (TES, July 19). One SENCO quoted in the study saw her task as “an M25 job, going round in congested circles” and Sheila confirms that there are conflicting demands.

“You’re battered from all sides, doing a juggling act between outside agencies, colleagues, parents and children.”

As a local president of the National Association of Schoolmasters Union of Women Teachers, she is aware of demoralisation in the professsion. “Ten or 15 years ago you never heard of teachers with stress-related illnesses, now it’s common. I have noticed that I am finding the work harder to deal with.”

Sheila is usually in school by 7.45am, often does not stop for lunch, takes several hours’ work home every night and feels too busy to swim or play squash, which she used to enjoy.

“All I want to do is collapse, although I know it would be worth making time to do exercise.”

At Floatworks she had to make time to do nothing. This is a pyschological barrier for chronically busy people as well as an organisational one, but Sheila was grateful for the opportunity.

Like many first-timers, she found that time plays funny tricks - the 50-minute session can seem like 50 hours or - once you’ve started to relax - five minutes. “I was still thinking about school for quite a while,” she admitted when she emerged, visibly refreshed. “I had just drifted off when it was time to get out.”

The real benefits of floating only bob to the surface when you’re showered, dressed and on the way home.

Sheila reported: “I felt wonderfully relaxed on the journey back, and pretty good the next day - possibly because it was the last day of term. I was disappointed that the relaxed feeling didn’t last longer, but I would definitely do it again.”

Tim Strudwick recommends a weekly float for “people with a lot going on in their lives”.

His theory that the benefits are cumulative was borne out by my second attempt - I relaxed more quickly, possibly because I managed to “let go” of my head and neck - ideally, the salt solution should cover the ears and the side of the face. I still worried about my ear plugs, but only briefly.

Sheila and I will be back - if we can only find the time.

Floatworks is offering TES readers 25 per cent off the price of a Pounds 20 peak-hour session (between 2pm and 10pm). Mention this feature when you book on 0171 357 0111. To find a reputable flotation centre in your area, contact the Float Tank Association 0171 627 4962