On one of the coldest days of the year, a headteacher had a bright idea: "Let's turn the heating off."
As temperatures plummeted to 1C (34F), pupils shivered in coats and scarves because head, Rob Benzie wanted to prove a point about saving the planet.
He switched off the radiators at Ansford Academy in Castle Cary, Somerset, to show how the secondary school could cut its carbon footprint.
But fuming parents and teachers got hot under the collar when they got wind of what had happened.
"It was absolutely ridiculous," said one teacher. "I've never worked in such cold. I'm all for saving the planet but this was barbaric.
A mum of a 12-year-old told the Sun: "She was shaking when she came home. I was absolutely furious."
A dad added: "Turning the heating off in December is just mental. I can't believe the kids learnt anything. I'm very angry with the school."
But Mr Benzie, 52, said the switch-off was a success and vowed to stage other "eco day" again at the 640-pupil school.
"We cut the heat to see if we can lower our carbon footprint. We let pupils wear as many jumpers as they liked," he said.
"Everyone seemed happy enough although it did get pretty chilly. We sent letters to parents telling them of the plan.
"We had only one complaint and that was from a member of staff. But in the end they just got on with it."