Teachers in Northern Ireland are being caused "a lot of stress" by websites which allow pupils to post their opinions of them, it has been claimed.
The sites allow pupils to rate teachers
Sites such as ratemyteacher.co.uk and bebo give pupils the chance to anonymously praise or castigate their teachers from their own homes.
Fern Turner, regional officer of the National Association of Head Teachers, said the situation was "unacceptable".
"We're talking here about teachers' professionalism," she said.
Among the posts on one of the sites, ratemyteacher.co.uk, were ones which read: "A useless piece of garbage who wouldn't know chemistry if it ran him over"; "She spends all our lessons on her mobile texting her boyfriend"; "I didn't like her as a teacher... she had a weird smell of vodka to her."
"The fact that somebody is making money out of attacking people isn't appropriate," Ms Turner said.
"I think part of being a teacher is training young children, and indeed sometimes adults, to respect others and respect their feelings and not to go out of their way to damage people.
"I think that is what this does," she said.
Ms Turner said her organisation did not condone bad teaching, but there were better ways to deal with problems.
"If the teacher is not doing the job it has to be dealt with, but it has to be dealt with properly.
"The website is not the way to do it," Ms Turner said.
"We need students to be active, we need them to be involved in their education, but this isn't the way to do it."