Exterminators were called to the Dean Academy in Forest of Dean in Gloucestershire to deal with the spiders, the Daily Mirror reported.
The story was the latest in a string involving the spiders, formally known as steatoda nobilis. They are believed to immigrated from the Canary Islands in the late 19th century, and experts say they may have become more common and to have moved north because of milder winters.
Some of the reports involve bites causing near-fatal injuries. Ricki Whitmore, 39, a decorator, said he spent three weeks in a hospital after a bite from a spider in an Essex school, while John Catlin, 66, said he was bitten in his garden in Kent.
John Tweddle of the Natural History Museum in London said bites are rare and most do not cause serious problems.
"If you are not keen on sharing your home with spiders, then it is best to catch and release them away from your home," he said. "Try to avoid touching the spider. As well as the small risk of a bite, spiders are easily damaged."
Tweddle recommends washing bites well. He said if serious symptoms develop it's time to get medical help.
Lawrence Bee of the British Arachnological Society said false widows are now common in south coastal houses and gardens:"Everybody in the coastal counties has had lots of them in their house and garden for many years, whether they have been aware of it or not."