Pupils in a British school have reportedly been provided iPhones to monitor the performance of their teachers.
The unnamed school in Kent insists it is a "quality assurance" programme.
Children can pass instant judgments to senior teachers on the quality of the staff.
The Association of Teachers and Lecturers are worried that the trend may catch up in other schools too.
John Rivers, a secondary school teacher, spoke on the issue at the union's annual conference in Manchester.
"There is a school in Kent brought to my attention by members where students are using school-issued iPhones to record their feelings during lessons," the Telegraph quoted him as saying.
He mentioned that almost 10 pupils of different ages were asked to email their comments about the quality of teaching directly to a central database.
He said: "There is an element of feeling that you are always being watched. 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."
The union insisted that it had the right to issue "clear guidance" on how lesson observations should be conducted.