Below is Paul Dix's answer to a behaviour question asked by a TES reader. The response was published in the TES:
The Problem
I have just started in a school and there is one class that is very noisy and easily distracted. One boy keeps shouting and two other boys act up and encourage him. How can I get them to settle?
The Expert View:
Ticks on the board and class punishments make an individual's behaviour everyone's business. Public humiliation encourages defensive reactions, creates an audience out of the class and builds up resentment quickly. Deal with the issue privately and calmly. Using fear and pure punishment might satisfy your own needs, but it will never meet the needs of your pupils. I don't want my pupils to be wary of me; I want them to be able to trust me.
Meet the pupil who is causing the most disruption and underline your boundaries with him. As you are new to the school you might choose to ask a more experienced colleague to sit in on this meeting. Tell the pupil precisely the noise level that you need. Describe it. A "three-bar voice" (from the volume setting on a phone) or a quieter "private voice".
You might choose to agree a cue for the pupil so that he knows when his volume control is appropriate and when it creeps over the limit. I have used volume crescendo bars to create a sign on the wall or a reminder on the desk that I can subtly refer to while teaching: "Clive, your five-bar voice is making my ears bleed, you need to bring it down to two bars."
Confront the behaviour and not the pupil. I once taught a pupil who would shout at full volume in private and group conversations. He wasn't seeking to disrupt, he was just loud. It was not until I visited his house and realised that eight people were living in a two-up, two-down that the penny dropped. Everyone shouted. He had learnt that unless his volume control was constantly on full, he might go unnoticed. Without referring to his home life, we managed to negotiate a diminuendo in learning time.