Children should be sent home from school if temperatures in classrooms soar, teachers' leaders have suggested.
Unions have called for a maximum temperature limit to be introduced, which would allow staff and children to be sent home if the heat becomes too much.
Chris Keates, general secretary of the NASUWT teaching union said said excessive temperatures are a "major problem" for schools, which are ill-equipped to cope.
"Pupils become extremely lethargic, unable to concentrate and in some cases faint.
"Lessons are disrupted by constant requests for time out to get drinks of water or to go outside and many tasks take far longer to perform."