As many as 24,000 children may have ME, now more usually called chronic fatigue syndrome by the medical profession. But both teachers and doctors are still often slow to recognise the condition.
The effects can be devastating, both personally and educationally. At primary school, Charlie Mogg was a keen swimmer who also played rugby union, and the trumpet. "You name it, he was in it," says his mother Joan Mogg.
Now aged 12, Charlie is too weak to walk, and has been for the last two years. Unable to bear daylight, he spends his days in bed, with the curtains drawn. A teacher's aide visits him for half an hour a week, "to give him a bit of gossip, make him feel he's still in the land of the living," says Mrs Mogg.
Education is out of the question. Although extreme weakness is the best known - and usually the worst - symptom, ME also slows the brain and interferes with the memory. Charlie is so severely affected that he can't keep up with stories on tape.
Other symptoms include muscle pain, sleep disturbance, and mood swings. This is how Action for ME describes the condition: "Imagine you had a severe hangover, plus daily influenza, muscle pain and exhaustion as though you had run a marathon, and could not think or comprehend anything for weeks, months or even years . . . this is what having ME is like."
The cause of the illness is still unknown, although the evidence points either to a persistent viral infection or a dysfunction of the immune system. Children with ME are often wrongly diagnosed as depressed, malingering or school phobic.
Charlie Mogg, three months into his illness, was referred to a psychiatrist after professionals suggested that he might be being bullied, although his physical health was worsening dramatically. One consultant suggested he be forced to go back to school, although he was so weak he had to crawl to the loo. "We knew it wasn't psychiatric," says his mother. "As a parent, the first thing you try is mind over matter."
But late or wrong diagnosis can make the condition even worse. Instead of being taught how to manage their illness by rest and pacing themselves, children are encouraged to "pull themselves together" and exercise their way back to health - a potentially disastrous course of action. "A patient who is not believed and therefore not able to take sufficient rest in the early stages of the disease is statistically less likely to recover than someone who is correctly managed from the outset," says Jane Colby, a former head teacher ME sufferer and member of the National ME Task Force Focus Group on Children.
Fifteen-year-old Matthew Ward of Cardiff, like Charlie Mogg, used to be a sports fanatic. As a seven-year-old, he played short tennis for Wales. "Everything he touched, he was good at," says his mother, Gemma Ward. But his health began to deteriorate while he was in junior school, and in 1990 he was diagnosed as having had glandular fever. Sport began to exhaust him but no specialist spotted the ME and he was advised to return to sport during the periods he was well.
By 1992, the year he began secondary school, Matthew's condition had become chronic. "It's been a nightmare for him," says Mrs Ward. "He hasn't been able to do any sport; he hasn't been able to function properly at all." Matthew can only manage two hours home tuition a week, although the local authority has offered more. His mother, a teacher, gave up her job 18 months ago to look after him after he fainted from the exertion of getting out of bed. He has not improved since.
The only treatments known to be effective for ME are time and rest. With the average duration of the illness in children four to five years, the effects on education are profound. Gemma Ward believes that particular forms of home education - in which the exertion demanded is reduced - could help. "With a lot of help from computers, television and the radio, I think children with ME could perhaps do more," she says. "But the teachers really are ignorant of this illness."
If sufferers exert themselves, they pay for it afterwards with increased pain and exhaustion. With their depleted energy levels, even children recovering from chronic fatigue syndrome find school difficult. Jane Colby, author of Action for ME's new Children's Charter, questions whether school is always the best place for them. "People think of school as a normal place for everyone to be," she says. "But if you're using up their mental and physical energy dragging round the building coping with social contacts, you're disadvantaging them educationally."
The point is not lost on young sufferers. "I used to be quite clever," says Matthew Ward. "But now my brain can't remember anything. I've missed out on an awful lot of work, and it's scary to think I won't be able to get a very good job."