A classroom teachers' union is challenging the practice of pupils sitting on job interview panels.
Student voice advocates say pupils will form opinions anyway
The NASUWT said the "student voice" was important but this failed to respect teachers' professionalism.
General secretary Chris Keates said the union had even come across pupils being trained to observe lessons.
But School Councils UK said probably most schools now had pupil interviewers of this sort and found it beneficial, and head teachers welcomed the idea.
Ms Keates spoke out after pupils at a Leicester school started to sit in on job interview panels for all new staff.
The policy is part of changes which have seen New College come out of special measures after Ofsted said it was failing.
Its principal, Jane Brown, said pupils were in effect the customers and it was important they have a say in how they were taught.
But Ms Keates said: "Regrettably, this is not the first time we have encountered this practice.
"It demonstrates a failure to respect the professional role and status of teachers and involves youngsters in a way which disempowers and deprofessionalises staff."
She added: "At this rate, it will only be a matter of time before someone suggests that pupils be trained as Ofsted inspectors."
Ms Keates said she had had a case in the north-east of England in which a teacher was being taunted by a pupil who had interviewed her, about things that had come up during the interview.
The union had advised its members "to challenge and oppose inappropriate student voice strategies" - and would support those who did.
There is no official guidance on the practice. Schools are however recommended to have student councils.
The charity School Councils UK, which promotes this sort of pupil participation, says the recruitment process for teachers often involves having them take a lesson.
It would be "naive" to imagine that pupils did not discuss the quality of the lessons they had had, and formalising this was a good idea.
"My guess is there would be more schools that are doing it than aren't," said spokesman Asher Jacobsberg.
As a head boy, 10 or 11 years ago, he had suggested that some of the prefects should interview prospective deputy head teachers.
The head had agreed and the school had found it so useful it was still doing it, he said.
Far from eroding the relationship between pupils and teacher, it was formalising it.
"It's unrealistic to stick your head in the sand and say this shouldn't be happening."
Head teachers postivie
Ms Keates said the pendulum was swinging far too far.
"We just think the time has come to pause and think what direction are these things taking us in, in terms of the pupil-teacher relationship."
But the Association of School and College Leaders disagreed.
General secretary John Dunford said it was not a new development, it was happening in a number of schools with very positive results.
"It is understandable that some adults find it daunting to receive pupil feedback, but the vast majority of schools that involve students in this way say that both the pupils and adults benefit.
"This does not mean the kind of generalised, unhelpful comments found on websites like ratemyteacher.com, but a structured process in which students are asked to make a constructive contribution," he said.