Teachers should avoid being too middle class in their efforts to get unruly pupils on their side, according to a good behaviour guru.

At a conference on behaviour last week, held by the Welsh Secondary Schools’ Association (WSSA) in Cardiff, Peter Walsh, a former assistant head, said flashing posh cars and acting aloof was likely to create a no-win situation in the classroom.

He has put together a guide on ways to gain the respect of pupils who smoke pot at lunchtime, wield knives and forget to bring pens to school. His top tips include ignoring pupils who are late to class, handing out more praise and showing a “human side” by genuinely asking pupils about their personal problems.

Mr Walsh, who taught for 36 years, has been researching pupil welfare and discipline for the past four years. He said: “Have you noticed how it is the nice-guy teacher that gets the better results - not the one who bellows at pupils in the corridor?”

However, he is not suggesting all teachers should be walk-overs. Instead, he believes they should remain quietly assertive .

Humour is also an important quality, as well as being able to diffuse situations with delaying tactics, says Mr Walsh.

More than a dozen teachers from schools with a mix of behaviour problems attended the conference. Mrs Lorenza Ciccione, from high-achieving Basseleg comprehensive school, in Newport, said: “I am here because we are now experiencing sudden behavioural problems on a scale we have not seen before.”

She claimed heads’ hands were tied when it came to procedures for excluding pupils. But Nicole Herberts, a science teacher from Queen Elizabeth high school in Carmarthenshire, said problems at the rural school were confined to a disruptive few.

A physics teacher, who asked not be named, said afternoon lessons were usually the worst. He said: “It’s often after the pupils put something funny in their Rizla during the lunch hour. Then they can find all sorts of things to do with the pens we provide because they don’t bring their own.”

Merthyr Tydfil-born Mr Walsh’s guidelines are based on the work of several leading academics in the field. He believes rights, responsibilities and rewards are the best way to tackle bad behaviour.

“However, there comes a time when enough is enough, when a disruptive pupil puts others at a total disadvantage,” he said.

Mr Walsh first became interested in behaviour management techniques in his 30s after he grabbed hold of a pupil by the scruff of his neck.

* Schools in Wales can exclude pupils as a last resort where there are extreme difficulties. Last month every secondary school in Wales was sent a handbook compiled by the Assembly government on classroom behaviour management techniques. Inspection body Estyn has also produced its own good practice guide for managing challenging pupil behaviour.