Peter Woods is a retired Melbourne high school maths teacher.
He is battling for teachers who appear on an American website called Rate My Teacher.
This website encourages students and their parents to rate teachers and to remark on their performance.
Mr Woods says that some of the comments on the website are nasty and are clearly intended to offend.
Teachers were being called "perverts", "sluts" and far worse.
Mr Woods noticed that young female teachers were often targeted by male students, with comments about their looks and speculation about promiscuity featuring heavily.
One female teacher was said to resemble "a horse".
One deputy principal was alleged to have "defecated in the school canteen".
One teacher was said to be a "wrinkly sack of poo''.
Another teacher was said to be ''a f---ing toss pot c---".
A male teacher was called "a vindictive homophobic racist bully who should never have been allowed to teach".
Mr Woods says that the comments on Rate My Teacher have been incredibly damaging for some teachers.
"A teacher I spoke to recently has been feeling suicidal," Mr Woods told news.com.au
Mr Woods decided that something had to be done about Rate My Teacher.
He signed up for Rate My Teacher himself.
He was eventually made a 'moderator'.
This allowed Mr Woods to approve other comments.
He was able to remove any comment that was unfair or nasty.
Mr Woods moderated comments on Rate My Teacher for the six months.
But when he told the Herald Sun what he was doing, he found that his Rate My Teacher privileges had been revoked.
He had been banned from the site.
So Mr Woods now urges other teachers to apply to become moderators on the website.
"I'm not normally a crusader, but this to me is just disgusting and it has to go," Mr Woods said.