Poor facilities, lack of money and pressure on curriculum time leave many schools struggling to teach pupils the most basic water safety techniques, three years after ministers promised to tackle the problem.
One school complained of cockroaches in the changing rooms. Another said it would be forced to halt lessons next year because the local pool was closing.
Drowning is the third most common cause of accidental death among children under the age of 16, with about 50 fatalities per year.
The survey of 587 primary, infant and junior schools in England and Wales was carried out in June and July by The TES and the Central Council for Physical Recreation (CCPR), an umbrella group for sports governing bodies and teacher organisations. One in 13 schools, mainly infants, does not teach swimming, even though it is part of the national curriculum for children aged five to 11.
Swimming is a legal requirement at key stage 2 in both England and Wales.
By age 11, English pupils are expected to have mastered four groups of skills, including survival techniques and the ability to swim 25 metres unaided.
An average of three in 10 pupils in each school fail to master personal survival techniques such as floating and using recognised swimming strokes by age 11.
Unless pupils in large primaries do much better than those in small ones, more than 100,000 children in England and Wales are left without these life-saving skills.
Despite this, less than half of schools offer remedial tuition to pupils who fail to meet national curriculum standards. And a third keep no formal record of pupils' achievements. Two in five schools ask parents for a contribution of up to pound;3.50 per lesson towards the cost of transport, pool hire or tuition.
Margaret Talbot, chief executive of the CCPR, said: "We think it is regrettable that many parents are being charged for part of the curriculum that is a statutory requirement. This should not be happening. Better school swimming would save lives. It is the only way you can reach all children."
The national curriculum only includes the bare minimum of survival skills, she added.
In 2000, ministers set up a task force to improve school swimming after a previous TESCCPR survey found that one in nine schools fails to teach more than half of their pupils to swim 25m - a finding repeated in this year's survey.
A report by the Office for Standards in Education in the same year warned that swimming was being squeezed out of the curriculum as schools concentrated on literacy and numeracy.
David Sparkes, chief executive of the Amateur Swimming Association, said that the Government has recognised the problem but schools need help to ensure that pupils have access to swimming.
A Department for Education and Skills spokesperson said: "Latest national statistics from Ofsted tell us that four out of five young people can swim the required 25m by the end of key stage 2.
"However, we know that there is still more to be done and there are measures that we have put in place to improve this situation."
These include a new swimming and water safety website, and ministers have promised to publish a swimming charter, setting out how much time schools should allocate to swimming, later this year. There are also two pilot schemes to give extra lessons to Year 6 pupils who cannot swim 25m.
The DfES spokesperson also said that swimming will benefit from the pound;459 million that the Government is investing in the school sport co-ordinator partnership to improve achievement in all sports.
David Hart, general secretary of the National Association of Headteachers, said that it was a tragedy that so many youngsters miss out on potentially life-saving skills.
"We have got to get away from the fixation with targets, tables and tests.
Schools should be given the autonomy and the funding they need to provide a proper, balanced curriculum. That has to include swimming," he said.
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