Specifically, the National Curriculum states:
Swimming and water safety
All schools must provide swimming instruction either in key stage 1 or key stage 2.
In particular, pupils should be taught to:
- swim competently, confidently and proficiently over a distance of at least 25 metres
- use a range of strokes effectively [for example, front crawl, backstroke and breaststroke]
- perform safe self-rescue in different water-based situations
Department of Education 2014 – National Curriculum
Should a child need to miss swimming for medical reasons, this is to be put in writing to the school explaining why the parent feels they should not take part.
Should the medical need be long term (more than 2/3 sessions), it is expected that a medical referral to a GP is made to ascertain a diagnosis or advise, on medical grounds, whether a pupil should be exempt from swimming on a long term basis. Such an exemption would not be agreed solely on a request from a parent, but should be supported with professional medical clarification.
Whilst we wish to support parents and meet their specific requests with reasonable steps, it is not possible to exempt children for the National Curriculum.
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/425601/PRIMARY_national_curriculum.pdf
http://www.legislation.gov.uk/ukpga/2002/32/section/78