Far from being a sedative or “chemical cosh”, Ritalin is a stimulant which, used in a small doses, modifies the behaviour and thinking of an ADHD child.

If taken in excess Ritalin can result in loss of appetite and disturbed sleep. It can also stunt growth, although this will recover again once the drug is stopped.

However, parents, teachers, psychologists and doctors are divided over the use of Ritalin. Some parents have found that giving the pill to children first thing in the morning means they can pack them off to school with the minimum of inconvenience. Some practitioners say that Ritalin could significantly reduce classsroom disruption.

However, others are uncomfortable with administering psychological drugs. They cite experiences in the United States where the behaviour of 2 to 3 per cent of children is being altered through drugs.

In Britain much of the Ritalin debate centres on Dr Geoffrey Kewley, an Australian paediatrician who has set up his own ADHD clinic in Horsham, West Sussex. He believes Ritalin can help ADHD children, many of whom he says are wrongly diagnosed as “naughty” and suspended or excluded from school.