One in four secondary schoolchildren with asthma cannot quickly use inhalers in an emergency because of policies of locking away medications.
Children are having asthma attacks on sports fields or in classrooms while their inhalers are kept in locked drawers in other parts of the school, the National Asthma Campaign said.
Asthma is one of the fastest growing medical problems among children. Each year between 100 and 200 die from severe attacks and many thousands of schooldays are lost through milder forms of the breathing disorder.
Martin Partridge, chief medical adviser to the campaign, said: 'It's quite ridiculous that children of secondary school age should be locked away from their inhalers.'
The National Asthma Campaign will write to the Department for Education this week to ask it to re- evaluate its policy towards the treatment of asthmatic children.
Dr Partridge said they wanted teachers to be given information to know how to deal with asthmatic pupils and every school nurse to receive training in asthma treatment.
The survey, carried out by Evelyn Smith at Bristol Royal Infirmary, found that only 7 per cent of school staff claimed to know a lot about asthma medication and that 74 per cent said they wanted to know more. 'We found that standards of care varied between different schools,' she said.
'While 60 per cent of schools had a procedure to deal with an asthma attack, 70 per cent had requested a short course on asthma and 90 per cent wanted more information. The most worrying factor was that many schools still insist on keeping children's inhalers locked away.'
Melinda Letts, director of the National Asthma Campaign, said inhalers were a first line of defence against an asthma attack. 'Teachers do not have to be doctors but knowing what to do if a child has an attack could mean the difference between life and death.'
The situation is believed to be far worse in primary schools because younger children are held to be even less responsible.
Faith Tuft's daughter suffered a severe asthma attack during a PE lesson at her London primary school. 'The teacher thought it was reasonable for her to finish the lesson as there were only a few minutes left, but by the time she had walked back to the changing room, breathing difficulties turned into a severe attack resulting in her having to be rushed to hospital.'