Pepe Di’Iasio, general secretary of the Association of School and College Leaders is is the former head teacher of Wales High School in Kiveton, near Rotherham.
He said schools needed to adapt their timetable to cope with the hot weather.
“Many schools are set up for children to be outside at lunch time in the hottest part of the day, come in and leave at certain times.
“What I’d be calling for is greater flexibility, the idea of agility in the school day at this time of year.”
Meanwhile, the Department for Education, states:, external “During hot weather, we don’t normally advise schools to close.
“This is because school attendance is the best way for pupils to learn and reach their potential, and hot weather can usually be managed safely.
A spokesperson, said: “School leaders should make sure they take any steps necessary to make sure children are safe and comfortable, and the heat-health alerts can guide this.
“Schools could consider relaxing uniform rules during hot weather to make sure pupils are comfortable.”
They added: “Children should wear loose, light-coloured clothing to help keep cool and sun hats with wide brims. When outdoors, encourage children to stay in the shade as much as possible.
“Sunscreen with high sun protection factors should be used to protect skin.”