Dr Rogers, the prodigious Australian-based author on classroom activity, said that nine out of 10 teachers he helped to mentor were often unaware of the impact they had as they spoke to children, moved around the classroom and responded to situations.

One of his principal jobs was to raise professional self-awareness, he told the national conference, organised by the Ethos Network at Edinburgh University.

“What is surprising is that teachers can be doing the same thing for years.

Like, ‘Are you supposed to be talking now? Would you like to come out and take the lesson?’ This teacher surely didn’t say that but she did. Where possible teachers should couch their language in positive, creative language,” Dr Rogers said.

Teachers had to be conscious of how they phrased questions and responses and avoid confrontation. They should intervene to stop behaviour that broke class rules and disrupted lessons, but often teachers were guilty of falling into wrangles that could be avoided.

He had worked with teachers who had seen pupils as constant threats. “One woman said to me, ‘I have to win’, but it’s not a contest. Forget the battles, you are the leader of the classroom,” he said.

Some teachers were far too non-assertive for their own good and others too confrontational, shouting at pupils and leaving them with few get-outs.

Illustrating the two types, Dr Rogers said: “There are some teachers who find it very difficult to confidently assert the appropriate leadership role in behaviour with young people. They know students will argue and challenge them and maybe even run off, but they do not engage.”

Some of them tolerated behaviour that should not be accepted, such as pushing and shoving or name calling. In one school he had worked in, as many as one in four staff might walk past incidents that affected the safety of pupils, such as fooling around in the technical department .

Students also played one teacher off against another, spotlighting their different approaches to discipline.

Dr Rogers, who advises schools in England and Australia, said: “I also work with teachers who are overly vigilant and cannot wait to score, and I mean score. They will not work with anyone. Some are also unnecessarily vigilant and when a kid comes in late, challenge them.

“I will acknowledge a student is late and speak to him later, but I will not ask him why he is late because at that point I don’t particularly care.

But some of my colleagues will immediately start this unnecessary contestability. For some teachers it often starts with this desire to exercise power over the kid. I’m not interested in having power over the kid; I’m interested in using whatever power I have with or for the kids.”

Dr Rogers said that “over and over again” he had seen small incidents spiral out of control leaving teachers with no option but to refer students up the disciplinary chain. Class teachers were sometimes only too happy to pass responsibility on.

Teachers should adopt a “relaxed vigilance” if pupils were late for class, annoyed others or disrupted the lesson. Pupils had to be made aware of the class and school rules and how their actions fitted in. Ownership of behaviour, even for pre-schoolers, and acceptance of responsibility for it were vital. “We want them to respect the fact that other people have basic rights,” Dr Rogers said.

Totally unacceptable behaviour such as sexually provocative language always demanded “necessary intervention”, even if students said they were only joking.

Students had to acknowledge as part of a behaviour agreement struck at the start of the year that drugs, weapons, violence and bullying were non-negotiable but most issues were negotiable, such as homework, lateness, uniform and talking out of turn.

Every school needed a time-out policy to allow students to calm down.

Teachers could not allow classes to be “held to ransom” but over the longer term such students had to be offered a personal behaviour recovery programme.

“In the last 10 years I have come across many, many teachers who will suffer in silence in the classroom. You can see them as you walk by; the class in catalytic conversion with noise levels you can hear up to 50 metres away. Some senior staff will stop and stare or barge in,” Dr Rogers said.

When classes were in meltdown, it was necessary to get the teacher out.

Where classes were frequently disrupted there had to be case supervision for the class with collegial mentoring.

Dr Rogers advised his 300-strong audience that it might take more than three years to develop a new ethos. Any child whose behaviour was frequently distracting or disturbing and more than “bad day syndrome” should be classed as having emotional and behavioural disabilities (EBD), but not necessarily in a clinical sense.