A teaching union has described increasingly draconian behaviour policies in schools in England as “inhumane” and “damaging to pupil mental health”.

The National Education Union (NEU), which is holding its annual conference in Liverpool this week, said zero-tolerance approaches to discipline were resulting in schoolchildren spending inappropriate and harmful amounts of time in isolation.

Anna Wolmuth, a teacher from Islington, north London, told the conference: “While classrooms may be calm, the referral rooms are full of Send [special educational needs and disability] pupils and pupils with things going on at home.

“There is an acceptance that this is what works without thinking of the impact on a child’s mental health.”

Parents have become increasingly concerned about the use of isolation booths in zero-tolerance schools. In some schools and academy trusts, children are removed from class and taken to a referral or consequences room, where they are made to sit in silence for up to six hours a day as punishment for breaking school rules.

NEU members echoed parents’ concerns. They backed a motion that said zero-tolerance approaches “promote surface-level compliance without addressing the needs underlying challenging behaviour”, and called for behaviour policies to be based first and foremost on pupil welfare.

Another delegate, Callum Wetherill from Leeds, later told journalists how he turned down a job as head of year after he was given a tour of the school isolation room and told he would be responsible for managing it. “Ten booths in a silent room. Where’s the education in this?” he asked.

“In some schools, if you turn round it’s an immediate detention. It’s the severity and the rigidity which I don’t think is good for any child.”

There was also concern among teachers that schools are overreacting to minor infringements. Sally Kincaid, an NEU activist from Wakefield, West Yorkshire, told of an 11-year-old boy who was sanctioned for saying thank you for his lunch when he was supposed to be silent. “They are not behaviour policies, they are punishment policies,” she said. “If you think that’s education, God help you, because I don’t.”

Delegates backed a motion calling for local authorities to be given oversight of behaviour policies for all schools and academies in their area. They also called for support for teachers who challenge “inhumane and unjust behaviour management practices” in their schools.

Opposing the motion, Stuart Allen, from Torfaen, south Wales, said it was sometimes necessary for children to be removed from classes because of disruptive behaviour, in the interests of the rest of the class.

“I am all too aware about the criticism some schools might attract if they enforce strong behaviour policies. But if a pupil is being disruptive, what about the other 29 pupils? What about their rights?” he asked.

Carole Buxton, a maths teacher from Hackney, north-east London, who has worked in special schools, told journalists that disruptive behaviour is often caused by complex needs. If a child has to be removed from class, they then need to be given support to cope with whatever has led to their difficult behaviour, she said. “The concern is they are just put into isolation,” Buxton added.

A Department for Education spokesperson said: “A school’s behaviour policy should set out the behaviour expected of pupils, the sanctions that will be imposed for misbehaviour, and rewards for good behaviour. This should be communicated to all pupils, school staff and parents.

“We are aware in some schools standards of behaviour remain a challenge. That is why the government commissioned Tom Bennett to conduct an independent review of effective behaviour. We recently announced a £10m investment, through behaviour hubs, to enable schools to share best practice on behaviour and classroom management.”