A hidden security camera in a secondary school has sparked concerns about child privacy.
There have been privacy concerns about cameras in schools
The head teacher of Walton High School in Stafford has written to parents to reassure them that children were not being filmed.
Staff placed the spy camera inside an office clock in an attempt to stop a series of weekend thefts.
Under local authority guidelines, schools are not allowed covert filming without permission.
The camera, discovered by contractors working at the school, was aimed at the office, but there were concerns that an adjacent classroom was in view.
Staffordshire County Council's Department for Education and Lifelong Learning said that permission for the camera had not been obtained from the head teacher, but that no pupils had been recorded.
"We are satisfied that the staff involved were not aware
of this and that their actions were well-intentioned but misguided.
"They have been told that there must be no repetition. No formal disciplinary action has been taken."
The use of visible surveillance cameras by schools has grown in recent years - particularly as security against the threat of vandalism and theft.
There were complaints from teachers' unions earlier this year when the King's Academy in Middlesbrough planned to introduce CCTV cameras within classrooms, which they said was an unfair intrusion into their workplace.
Among the arguments in support of using of cameras was that it gave teachers protection against false allegations from pupils.
The use of CCTV cameras within school has also been suggested in other areas as a way of catching bad behaviour among pupils.
In Arizona in the United States this month, the first "face scanner" in school has been introduced, which uses hi-tech security cameras to compare adult visitors' faces to a database of the faces of sex offenders.