A Victorian painting - bought for under pound;300 - which had languished in a hallway for decades, has provided a Welsh comprehensive with the funds to replace crumbling science labs.
The Daughters of Eve by Victorian artist George Dunlop Leslie, had hung for 40 years in the entrance hall of Llantarnam comprehensive in Cwmbran. Unfashionable when it was bought, the painting was noticed by few at the school, and liked by even fewer.
"It was a classic chocolate-box painting," said David Kitchen, Llantarnam's head. "The youngsters knew it was there, because they noticed when we removed it, but they couldn't say what it was."
The eight-foot painting had been purchased by the school's architect in 1953, to counter what he felt to be the harsh modernity of the building. He paid less than pound;300.
When, over half a century later, Mr Kitchen decided to have the painting valued, it came as a shock to discover that it was worth at least pound;60,000. "It was unexpected. I began to think, that's a lot of money to put on a wall," he said. As budgets were stretched, he began to wonder whether the painting might not be transformed into a more useful asset.
He took it to auctioneers Sotheby's. It was subsequently sold for pound;170,000 to a primary-school teacher from a family of collectors in New York state. The money has gone towards the pound;245,000 costs of a new science block, including physics and chemistry labs, and a multi-purpose classroom.
"I think we had the better bargain, definitely," said 15-year-old Anthony Phillips, one of the pupils who has since made use of the new labs. "The old labs were falling apart: there were holes in the floors and in the windows. Now they're all modern, nice and bright."
A full-size reproduction of the painting now hangs in the entrance hall. "Children can still look at it, and they still don't notice it," said Mr Kitchen. "Though I think they look at it a bit more closely now they know it's become a science block."
Llantarnam is not the first school to discover hidden treasures. In December2001, Buile Hill high, in Salford, was looking to fund a bid for arts college status when they discovered the school owned an LS Lowry painting.
They hope it will fetch pound;20,000 in auction and they will also sell two paintings by Lowry's pupil Harold Riley.
This month, public school Charterhouse auctioned off part of its archaeological collection, to fund better library and computing facilities. The school, fees pound;19,080 a year, raised over pound;700,000 by selling prehistoric and other objects, and pottery.
Works by renowned artists have turned up in schools in Ireland and Connecticut. "Often paintings are found in places you wouldn't expect," said a spokesman for the National Gallery. "But they tend to be in old churches. Finding one in a school is quite unusual."