Imagine setting off to teach every morning knowing that you will not be able to have a drink for at least four hours, unless you are desperate enough to stand in toilets with Victorian plumbing and place your mouth over a spout sucked by generations, not to mention your colleague with a streaming cold. It is a nightmare you are unlikely to experience, but for millions of children it is a reality of school life. In 2002, the toilets were the only source of drinking water in half our schools, according to the Health Education Trust. So children who need to run around for exercise at breaktime risk all of the uncomfortable and unhealthy side-effects of dehydration.

It is a situation that the Enuresis Resource and Information Centre (Eric) has been working to change. Eric is a small children’s medical charity based in Bristol, but since the launch three years ago of its Water is Cool in School campaign, it has persuaded thousands of primary schools to rethink their drinking water policy.

Through leaflets, posters and personal talks, Eric, with various partners, has made heads, teachers, parents and pupils aware of the dangers of dehydration and the ease with which it can be combated.

Dr Jonathon Darling, a consultant paediatrician at St James University Hospital in Leeds, became involved in the Cool in School campaign after his experiences in clinics. “I was seeing children with kidney problems, urinary infections and constipation, which can all be linked to not drinking enough water,” he says.

“There is also evidence linking adult bowel and bladder cancers to lack of water. Regular drinking throughout the day can certainly make all the difference. A glass of water before leaving the house, one at break, one at lunch and another in the afternoon is all it takes.”

Another medical benefit of drinking more water is that it takes away some of the urge to drink fizzy pop or sugary squashes. “Water is the only drink which you can have as much as you like and not harm your teeth in any way,” says Dr Darling. Nor does it harm your waistline. A 2001 report in The Lancet warned of a 60 per cent risk of obesity for every can of high-sugar drink a child consumes in a day.

Eric’s message echoes the medical advice: allow and encourage children to drink little and often throughout the day. This has obvious implications for schools with old water systems or those used to placing strict controls on children’s bodily functions. But the vast majority of schools that turned to Eric for advice have found that most problems are surmountable and the benefits outweigh the logistical concerns.

If the long-term health of pupils is not necessarily the first priority for schools, achievement certainly is. And again water can play an important role in improving standards, according to Accelerated Learning in Training and Education (Alite). Its teaching methods concentrate on how the brain works and emphasises the part played by water. Its website points out that the brain is 80 per cent water and that dehydration of just 1 per cent can result in a 10 per cent decrease in mental performance.

A big worry for many schools that contact Eric is expense - how much will a constant supply of cold, palatable water cost them, in terms of money and the time taken to police it. Schools have tried several methods. One option is to install a mains-linked water cooler or fountain in a corner of the school not connected to the toilets. Schools then allow regular trips to the cooler to drink or to fill up bottles. Others have turned to expensive supplied cooler bottles despite the proven high quality of tap water. Yet more schools have just relaxed their attitude to water in the classroom and have provided bottles or let children bring in their own from home.

Beverley Leeson, Eric’s deputy director, believes that whatever schools choose to do, the costs can be minimal. “It is up to schools to decide how much they want to spend,” she said. “I believe it costs around pound;300 to have a water cooler plumbed into the mains, but asking parents to send in a bottle of water each morning with the children costs next to nothing.”

But Ms Leeson warns of long-term implications. “When costing a project, schools have to think of the ongoing maintenance costs, or how they will keep water bottles clean and hygienic.”

Although Eric’s main influence has been in the country’s primary schools, secondaries are now showing an interest, particularly as pupils move up the system. “There has been a definite upward pressure from children leaving Year 6 with the expectation that they will be able to continue to drink water throughout the day, and a number of schools are responding to that pressure,” says Ms Leeson.

For more information: www.wateriscoolinschool.org.uk orwww.alite.co.uk.

Education Communications, with input from Eric , is researching water provision for the Department of Health’s Food in Schools programme and the Health Education Trust (see story, right) is looking into food vending