A teacher has been humiliated on the internet after pupils secretly recorded him performing a 'funky chicken' dance as an end-of-term treat.
The exposure of Phil Ryan on YouTube has prompted a warning to teachers about the risks posed by new technology to their professional standing.
The science teacher impersonated a chicken as part of an act to entertain pupils at Broadgreen International School in Liverpool on the last day of term.
But a student secretly filmed the performance on his mobile phone before sending the clip to a friend, who forwarded it on to others.
It has now been viewed more than 6,000 times after one of the recipients posted the film on video-sharing site YouTube.
While some viewers hailed the teacher's sense of humour, many others posted mocking and derogatory comments.
The incident is among a catalogue involving teachers that has led classroom unions to plan special workshops on the risks of being compromised by new technology.
A dossier of cases compiled by the National Union of Teachers includes a member whose homemade explicit tape was posted on a social networking site by 'an aggrieved party in an act of vengeance'.
In another incident, a teacher left a memory stick containing suggestive photographs at school. Fortunately for them, a colleague rather than a pupil found it.
In a third case, a teacher needed advice from the union after railing against a senior member of staff on Facebook.
0ther staff have been subjected to abusive text messages after giving out their mobile phone number as a point of contact for coursework queries.
Advice for teachers on how to avoid being compromised by the internet and mobile phones will be included in induction sessions for new recruits, initially in Liverpool.
Julie Lyon-Taylor, NUT executive member for Merseyside, said many young teachers were comfortable with technology but may not realise its risks.
'Because they use it all the time they may not realise what they might be leaving themselves open to,' she said.
'It is about educating the young teachers as we want to avoid these incidents which could affect their professional standing or put them in a vulnerable position.'
The union nationally is also keen to raise awareness of the threat to teachers of material being used against them.
John Bangs, the NUT's head of education, said it was 'a tragedy' good teachers could not even relax and enjoy a joke at the end of term for fear of it ending up online.
'Something like this can really undermine a good teacher, but the only way round it is not to expose yourself in the first place. There are downsides to living in an IT-literate age,' he said.
Ian Andain, head teacher at Broadgreen and chairman of Liverpool Schools Forum, said: 'Technology has completely changed the way in which people need to present themselves, and make sure they aren't vulnerable to humiliation.
'Something like this was funny at the time but once it's on a website you can end up with all sorts of malicious comments and the whole situation escalates.
'Posting your profile on things like Facebook is so risky for teachers as it is a huge manifestation of your private life.
'Something done for the amusement of students is not something you necessarily want on a website used by millions of people.'
The clip of Mr Ryan squawking as he pretends to be a chicken was filmed by pupil Andy Hirrell, 18, who has just left Broadgreen and is about to start at university.
He says he sent it to just one other person but before long it had spread around the school and ended up on YouTube.
'Someone asked him to do it and he said he would because it was the last day of term,' he said.
'It was out of the blue because he was so strict.
'I couldn't watch it because I was laughing so much. I had to put my head down and leave my camera on my desk.'
Mr Ryan was apparently asked by pupils six months later to repeat the stunt but said he wouldn't because his last attempt had ended up on Youtube. The teacher retired last summer.
Mr Hirrell admits phone cameras were banned in school but says he was taken aback by the clip's popularity.
'I thought it would be something just our school would know about,' he added.
Research by the NASUWT union on the scourge of so-called 'cyber-bullying' revealed that 20 teachers a day are reporting incidents involving pupils who use mobiles or the internet to spread offensive remarks and images.