Primary teachers are forbidden from applying suntan lotion to younger pupils, even if they show signs of going red, because of fears of possible allergic reactions.
But as outdoor learning - an essential part of the play-led foundation phase - becomes more frequent, teachers are becoming more concerned about the health risks of prolonged exposure to the sun, particularly with children of nursery-school age who burn easily.
Alyson Roberts, head of Romilly Infants and Nursery School in Barry, Vale of Glamorgan, said it had invested pound;14,000 to provide shelter. The school has sent out letters to parents reminding them to provide their children with suntan lotion as well as a hat or cap.
Ms Roberts says she believes children as young as three should be taught how to apply sun cream.
Iwan Guy, acting director of the National Association of Head Teachers Cymru, said sending out warning letters was the only action teachers could take. "Teachers can no longer put sun lotion on pupils themselves for health and safety reasons - it is a problem if a child burns easily," he said.
Some schools have invested in sun cream dispensers, or given children sacks with cream and a legionnaire-style hat to protect the neck. But many ask parents to bring in their own bottles.
Angela Morris, head of Tregwyr Infants School in Swansea, said: "We also ask parents to send in summer hats and something with long sleeves," adding that parents were asked to put cream on their children before school, even when the weather was not great.
Laura Warren, communications manager for the National Confederation of Parent Teacher Associations, said many schools had relied on parents to help fund wooden or canvas shades.
But she said most parents realised the health risks of exposing their children to the sun and sent them to school well prepared.
Ms Warren said children who have been playing with water, or those with very fair skin, may need to have their cream reapplied.