Schools are snooping on social networking sites, and googling potential candidates before appointing new staff, teachers have been warned.
Teachers should be wary of what they post online and check what information is available about them, a fringe meeting at the National Union of Teachers (NUT) conference in Harrogate heard.
Karl Hopwood, an online safety advisor said he was aware of a number of cases where schools had checked up on teachers through the internet.
In one case, he said, a group of newly qualified teachers had had trouble gaining jobs.
The feedback they got from one head was to look on their networking sites. One of the girls concerned had a picture of herself with a pint glass on her head.
"You wouldn't think this was the end of the world," Mr Hopwood said.
But after the teacher changed her settings and removed photos she did get a job, he added.
In another case, Mr Hopwood said he was part of an interview panel.
"The chair of governors handed me an envelope of stuff from Google," he said.
"It was of everybody going to interview and she said this was what they had found out about them."
The chair had told him that they had to get the right person and if they could find out more information to help them, then that is what they would do.
Mr Hopwood cited research that had shown that more that half of UK companies would do online research of prospective employees.
Often links to photos on social networking sites can appear on internet search engines, he said.
He also warned teachers against making friends with pupils online, as they may be able to see images or information that teachers consider to be private.
"Private and public life is blurred now," he said later, we have to try to manage it."
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