A Victorian school building officially opened last week after undergoing a £1.2m renovation.
The old Chestnut Grove Academy building, in Chestnut Grove, Balham, has new windows, a boiler and complete roof renovations.
It also has a new boiler, skylights and large windows crafted to match the existing Victorian ones.
The old building suffered from windows falling out and draughty classrooms, with the school granted money for a renovation when it became an academy last year.
MP Sadiq Khan cut the ribbon to officially open the renovated building.
He said: "Your school is one of the best in the country. Don’t just take my word for it - independent people have said Chestnut Grove is in the top two per cent.
"And you are an outstanding school according to the inspectors.
"And if you were outstanding when you had windows falling out and draughty classrooms just imagine what you can do in these fantastic surroundings."
Heateacher Margaret Peacock gave a history of the school and said she was determined the building would not be demolished.
She said :"What’s really good is that we were not only able to replace the windows and boiler but also to do all kinds of improvements to restore what I think is a really beautiful building."