* Pupils use YouTube to post embarrassing videos of teachers
* heads say 'web rage' should be a disciplinary offence
Every teacher has classroom moments they'd rather forget. But imagine having your humiliations broadcast to an audience of thousands over the internet.
This is the nightmare scenario endured by an unlucky minority of British teachers, who have had their lessons from hell posted on video website YouTube. Now, 18 months after the popular site was launched, teachers unions are calling on it to clamp down on this form of "cyber bullying".
The site is attracting 32 million users worldwide a month... and counting.
This week it was bought by Google for pound;883 million. YouTube has proved increasingly popular with British teenagers who log on to the site to view funny clips from around the world and watch YouTube "celebrity"
video bloggers such as lonelygirl15 and Ask a Ninja. They can share their thoughts on everything from "ninja grub" to film star George Clooney.
The ubiquity of mobile phones with in-built cameras has meant that a small but growing number of teachers are finding themselves unwittingly targeted by malicious posters.
And while some clips are frivolous - teachers dancing or performing ill-advised vocal numbers in front of a baffled class - others are plain nasty.
Recordings show teachers being sworn at, mocked, imitated, and in one particularly embarrassing case a male teacher has his trousers pulled down while standing with his back to the class.
Most filming is done surreptitiously and posted on the site without the teachers' knowledge, often alongside cutting remarks or innuendo.
Mick Brookes, general secretary of the National Association of Head Teachers, said: "It shows a complete lack of emotional intelligence. Behind the cover of the internet, people feel they can act as they wish. It's like road rage in cars, only this is 'web rage'.
"There is no reason this should be outside the remit of school discipline.
Pupils who engage in this behaviour should be punished."
A spokeswoman from the National Union of Teachers said the internet companies should take action and stop the postings.
Some of the worst entries on the site include homophobic bullying: one video is prefaced "Big Gay Al getting abused". Another shows long close-ups of a female teacher's cleavage ("sexy high school teacher from a high point of view overlooking her breasts") and one post titled "f*** off Mr Corrie"
published two months ago which shows secondary school children directing obscene gestures and insults at their geography teacher.
Other less serious postings are devoted to the age-old pastime of exposing teachers who attempt to get "down with the kids".
Spare a thought for "Tozzer", the singing RS teacher, with his unique educational ditty "get Socratic not erratic" (complete with dance moves), or the science teacher from Luton who thought it would be a good idea to make a song about electrons based on Abba's "Waterloo" ("this teacher ain't got a clue!" says one blogger).
But while such videos may seem like harmless in-jokes, most are posted online without the teacher's permission.
Blogger pimpom88, 18, who set footage of her middle-aged Latin teacher to Bonnie Tyler's "Holding Out for a Hero", told The TES: "He doesn't know the video exists. I don't think I'd like him to see it. We were bored one day after school and just did it as a distraction.
"I suppose you could say we were taking the mickey somewhat, but we're very fond of him, although he's a little out of touch with the 21st century."
Earlier this year the site Rate My Teachers also caused concern, after pupils used it to complain their teachers were "pants" and "power-hungry"
while rating them for the quality of their lessons.
The misuse of information and images online is a legal grey area, with most of the responsibility lying with websites themselves to informally monitor content. The US, where many websites, including YouTube, are based, has less stringent privacy laws than Europe, meaning that bringing a case for breach of data protection or confidentiality can be difficult.
However, it is not all bad news for teachers who find themselves bathing in the unwanted glow of YouTube celebrity. Some grateful students use the site to celebrate their favourite teachers.
Even the benighted Tozzer is not without his fans: one female blogger exclaimed: "We love Tozza! He was so blatantly the best teacher!" Other students have used the website to post fond farewells to favourite members of staff.
Nobody at YouTube was available to comment.