Experts are warning that youngsters are being exposed to dangerous amounts of UV radiation from sunlight because of a lack of shaded areas in schools.
The report raises fears pupils are not being properly protected and could suffer from skin cancer in the future unless procedures are changed.
The survey of 345 primary schools found that 44% have no shaded playground areas, despite many outdoor activities being scheduled between 10am and 2pm, when the sun is at its strongest.
The British Association of Dermatologists, which commissioned the study, said 95% of schools do not have a defined sun protection policy, although 80% of staff think they should.
Dermatologist Mary Laing said: "Skin cancer is the most common type of cancer worldwide. All types of skin cancer are largely preventable through limiting exposure to UV radiation in sunlight.
"Schools are an appropriate venue for sun protection programmes as learning sun protective behaviour at school may lead to protective behaviour outside school also."
The survey also reveals that only 24% of schools include hats as part of their uniforms, but 55% do allow pupils to wear sunglasses during outdoor activities.
Nina Goad, of the British Association of Dermatologists, said: "It is thought that just a couple of cases of sunburn as a child could as much as double your chance of getting skin cancer later in life."