The Scottish Secondary Teachers' Association raised its concerns with West Lothian last December amid fears that images may be misused. Pupils could be unaware they were being photographed.
David Eaglesham, union general secretary, said: "It is possible for kids to use them in the shape of bullying but perhaps more sinister than that it can be used by paedophiles. If they get their hands on these images then there will be a great problem."
One teacher said: "Staff support the ban, not least because they don't want their pictures appearing on the web." Some schools have already banned phones and personal stereos. As well as being distractions, they can be stolen and arouse jealousies, another said.
Peter Wright, SSTA representative in West Lothian, said: "In past months, I have dealt with a number of cases where teachers were photographed without their permission, thus causing disruption to teaching and learning, in addition to the invasion of teachers' privacy."
If the ban is breached, Mr Wright said, teachers and managers now know they can take appropriate action.