The Rate My School site, similar to the controversial Rate My Teachers, allows staff to score schools on everything from behaviour to staff morale.
Its logo is "Where teachers tell tales out of school".
Critics fear it will become another platform for cyber-bullying.
Co-founder Chris Sivewright said the site will be indispensable, particularly for supply teachers and new trainees.
He said: "There are things that job adverts can't tell you, like levels of staff morale and behaviour. Is the headteacher an ogre? What is the flick-knife to pupil ratio?
"I've worked at schools that have very good reputations but the staff are bullied and terrified. These are important things to know before you take a job."
The site allows teachers to score schools on behaviour, morale, the quality of the buildings and even the school canteen. Staff can post general comments, but users must email each other to obtain detailed information.
Mr Sivewright said there was a ban on naming staff to avoid falling foul of libel laws.
The site was set up after a thread on The TES online staffroom found some teachers supported the creation of a rival to Rate My Teachers, allowing staff to "dish the dirt" on their former workplace.
Rate My Teachers, which allows pupils to review their teachers, was condemned by unions after pupils used it to dub staff as "pants" and "power hungry". Other postings have been pictures of teachers' cleavages and some footage showed a teacher having his trousers pulled down.
Calls for such websites to remove videos and images of school bullying were applauded by teachers at the NASUWT conference in Belfast. Alan Johnson, the Education Secretary, demanded that providers of websites such as YouTube and Bebo took firmer action to block offensive material.
Ian Rivers, a professor of psychology at Queen Margaret's University, Edinburgh, is running a study looking at how 3,000 11- to 13-year-olds use hi-tech tools such as email, mobile phone messaging and sites such as Bebo.
He told a fringe meeting at the NASUWT conference: "What is striking is the increasingly sexualised nature of cyber-bullying between pupils."