By Katherine Sellgren
BBC News education reporter at the ATL conference
iPhone applications are being used on trial in other schools
Pupils have been given iPhones to give instant feedback on lessons, a teachers' conference has heard.
iPhones were handed out at a secondary school in Kent as part of a "quality assurance" week, the Association of Teachers and Lecturers was told.
Pupils were encouraged to write comments about teachers and opinions about lessons and send them to the senior management at the school.
The union said gathering feedback in this way "lacked transparency".
Backing a conference motion calling for better guidance on how pupil observation was conducted, John Rivers, an information and communications technology (ICT) secondary school teacher from Kent, said he was contacted for advice by colleagues at the unnamed school in question.
Mr Rivers said the scheme raised a number of concerns.
"How were the students chosen? What training or advice were they given? Were they given carte blanche to comment on anything?
"I have no problem, generally, in asking pupils about how they felt about my lesson.
"It is just that I believe there should be clear guidance on how these observations should be conducted and reported."
Lack of transparency
Speaking later, Mr Rivers said teachers at the school were concerned that they had not been forewarned of or consulted on the scheme.
"I understand it just happened. Staff at the school were not aware of how it worked. There was a lack of transparency."
He said these sorts of initiatives could make teachers feel they were being watched.
"I suppose staff must feel it's a bit threatening, if it's not transparent."
The teachers did not know whether or not they would be given a right to reply or see the comments, he added.
The ATL voted in favour of a resolution calling for the union to issue guidelines on how lesson observations by pupils should be carried out.