A company which built six new schools in Exeter has been summoned to a meeting with head teachers - who are complaining the classrooms are too hot.
Three of the schools were delivered behind schedule
The schools, which were constructed under the private finance initiative, do not have air conditioning systems.
Students say the schools are too warm to study in, with some reaching temperatures of 33C (91F).
Carillion PLC said it built the schools Devon County Council specified, which did not include mechanical ventilation.
The schools were built without air conditioning to make all its new developments environmentally friendly.
St Luke's Science and Sports College
West Exe Technology College
Isca College of Media Arts
Wynstream Primary School
The leader of Devon County Council, Brian Greenslade, said: "I think it's an approach we've always taken not to provide air conditioning in our schools or ventilation measures, but we are keen to overcome the issues which are plaguing our new schools at the moment."
He said the council has withheld payment to the company, believed to be a six-figure sum.
"We believe there are things Carillion can do to deliver the contract, but we are concerned that so far they haven't shown the degree of response that we want to see."
Carillion said it was looking into re-jigging the schools.
The schools have been dogged with problems - three of them were completed four months behind schedule and St Luke's had to call in pest control after an outbreak in fleas.