Vincent Capaldi, deputy head of Wimbledon College School for boys, said the teenagers were banging on the roof of the bus and chanting obscenities. All the boys, who were wearing school uniform, received temporary exclusions.

Mr Capaldi said he spent half an hour every month searching YouTube for text making reference to the school.

He said that, until now, videos uploaded to the site by students had been of an amiable nature and included rugby matches and sixth form social events. The offending video only came to light when one of the culprits mentioned it to a teacher. The boy who uploaded it was identified and agreed to remove the clip.

A spokesman for Google, which owns YouTube, said the site had guidelines to stop invasion of privacy, which included cases where teachers had been victimised by pupils. “People can flag inappropriate content and our staff then review it,” he said.

John Bangs, head of education at the National Union for Teachers, said he was glad schools like Wimbledon College were proactive, but was sorry teachers now had to spend time searching websites. “Internet providers may not see how undermining it can be for schools when images of bad behaviour or bullying are flashed around,” he said.