Scottish teachers have called for action to be taken to stop pupils "cyber bullying" school staff.
The SSTA says teachers have been insulted on websites
Some websites encourage pupils to submit anonymous "reviews" of their teachers' performance.
The Scottish Secondary Teachers Association said the sites often hosted insulting comments that were left in an attempt to humiliate staff.
The union said all material should be monitored to ensure it was suitable before being made available to view.
The SSTA also called for video hosting sites like YouTube to crack down on pupils who post footage of teachers that has been filmed in class on mobile phones.
The US-based RateMyTeachers website carries comments about individual, named teachers.
Remarks left on the site have included: "I have heard awful rumours about that man" and "he is evil personified".
Both YouTube and RateMyTeachers agree to delete material if they receive a complaint, but Ann Ballinger of the SSTA said it was often too late to prevent teachers being embarrassed.
Speaking ahead of the union's annual congess which starts on Friday in Aviemore, Mrs Ballinger said: "They can be so destructive. They can damage a teacher's professional life, damage their home life and they can cause huge upset to the teacher and their families."
Mr Ballinger cited a recent example when the son of a male teacher read comments on the web questioning his father's sexuality and accusing him of having inappropriate relationships with other members of staff.
Last month, teachers in England threatened to sue websites that allow pupils to post abuse and humiliating video clips and photographs of them on the internet.
The Association of Teachers and Lecturers said some of its members had considered leaving the profession because of the extreme distress the sites had caused them.
But Stuart Waiton, director of child rights organisation Generation Youth Issues, said teachers should learn to develop thick skins.
He added: "In the past, teachers would tell children that sticks and stones might break their bones but words will never harm them.
"Now it seems that teachers are acting like children who are easily offended by the gossip of school kids.
"If teachers are so chronically offended I would suggest they go and get another profession."
A video circulated among pupils at Hawick High in January showed the school's new headteacher being punched in the face by a teenage boy.
Elswehere, footage appeared on YouTube of a pupil pulling down his teacher's trousers in a classroom in Cumbernauld while his friends filmed it on a mobile phone.
A female teacher discovered that a photograph of her face had been superimposed on a naked body and circulated on the web.
Another teacher learned that a female pupil had posted lies about her sex life.
Photographs of teachers' cleavage or underwear have also been made available to view on the internet.