Children at school named the most technologically advanced in the country are wearing coats in lessons because the heating does not work properly.
Sutton Council has said problems with heating in the £50m state-of-the-art Stanley Park High School's new building is down to teething problems and work is under way to fix the problem.
But a source close to the school, who asked to remain anonymous, said big open spaces in the Carshalton school had not been adequately heated all winter meaning large parts of it have been very cold.
The source said: "There is still no proper heating at the school which is quite a concern as they are going for academy status. As far as I am aware the receptionists and admin and some classrooms are still very cold and will get colder with snow on the way."
Conservative Councillor Tony Shields added: "The heating doesn't work - there are kids there in coats. They've installed a substandard heating system which just isn't suitable."
Stanley Park was named the most technologically advanced school in the country after it opened its £38million redevelopment last year.
It has won prizes for its design including the ACE Engineering and Excellence award specifically for its heating and electrics.
Coun Dave Callaghan, chairman of Sutton's Children, Family and Education Committee, said: "Stanley Park High School has been built to the latest design and building specifications and whilst savings were made to offset road, land and legal costs the heating and electrical design for the school did not change.
"However, as with all new schools there are teething problems and there is now a programme of work under way to rectify the faults."