It’s the teacher’s first lesson and he greets his new class by drawing a line on the board. “What’s that?” he asks. “It’s a line, sir,” the pupils reply. “That’s right,” he says. “Now just make sure you don’t step over it.”

This was a story told by a teacher at a further education college, and it neatly illustrates how consistency works.

There is a metaphorical line over which the pupils must not step: this line is fixed and should not move. It is in the nature of young people that they will try to get you to move your line - they will push at the boundaries to try and get away with just that little bit more. And more. And then even more.

In the short term, being relaxed about your line can make life easier for you. But soon the children realise that you can be manipulated, and they start to shove the line in all directions. Having one relaxed teacher who wants to be the pupils’ friend makes life harder for other teachers. Miss Smith says “No gum,” and imposes sanctions on those who chew. If Miss Jones says “Go ahead and chew,” this makes Miss Smith look unreasonable.

In my own first year, I made the mistake of letting the line slip. The class was updating Shakespearean text, and they began to push at the linguistic boundaries. Or, in plain English, they tried to slip in some swearing. Although the resulting scenes were engaging and vividly performed, my mentor sensibly warned me to destroy any written evidence after the event.

Where the line actually lies will vary according to the pupils you teach and the kind of school where you work. There are some behaviours where the line is obvious - fighting is never acceptable. But in some schools, there is also a rigid emphasis on relatively minor areas, such as correct uniform. Where the whole staff works together to enforce the rules, it can be surprisingly easy to get the pupils to comply. But if one or two teachers let things slide, before you know it there will be wide-scale rebellion.

Children really appreciate the structure and security that consistent boundaries offer. They want to know what to expect from you, and also what you expect from them. It’s a question of fairness and of treating all children reasonably and equally, no matter our personal feelings about them.

Senior managers strive for consistency between teachers across a school.

What they want is for a child going to any lesson, with any teacher, to be met with the same expectations of attitude, work and behaviour. It’s fairest on the pupils, and plays a key part in creating a positive, whole-school ethos.

As a professional, you need to put aside your personal opinions about whether the rules are fair or reasonable. This is much easier to do when staff are involved in drawing up school behaviour policies. They should be given their say in what they can and cannot ask the pupils to do - after all, they know the children best.

There will be occasions when you might want to move your line a little, bending the rules rather than breaking your relationship with a child or a class. Maybe you teach a totally disaffected Year 11 bottom set. The handful of pupils who occasionally produce some work are chewing gum. Is it worth being consistent and cracking down on this, or is would such a course of action only further alienate these pupils from you and your lessons?

In your NQT year aim to fix your line in place early and show your pupils that there is no point in pushing at it. That way you can get on with the most rewarding part of your work - the teaching.

Sue Cowley, a behaviour management expert, is the author of ‘How to Survive your First Year in Teaching’ (Continuum)

‘I ended up with complete chaos’

Sian Woolaway teaches science at Kendrick school in Reading

I’m an NQT in secondary science, and started my PGCE last year wanting to be laid back and relaxed. I tried to be consistent as I had been told it was important, but it didn’t work.

If a child approached me during a lesson and asked to print something off in the IT room, or to get a merit sticker for doing something quite well, I would think ‘Well, if it’s just the one, it won’t hurt’. I ended up with complete chaos as everyone else slowly cottoned on and started pestering and complaining.

I’ve learnt my lesson the hard way, and have started all my classes off on the right foot this year, with a clear rewards, rules and sanctions sheet.

I am determined to stick to it and apply it fairly and consistently.

‘I constantly repeat myself’

Tracey Dunn is deputy head of Priestley primary in Calne, Wiltshire

A consistent approach in the classroom and throughout school has led to improved behaviour and attitudes to work. It helps children learn to use their initiative. Taking time to establish routines and to share expectations enables children to succeed. It is hard work and I find I have to constantly repeat myself, but it is always beneficial. I realised one morning that I didn’t have to remind or ask, and that children had the confidence to use their initiative.

I have found that consistency works regardless of the age or ability of the children. They know where they stand with me: that they will be treated fairly and that I follow through with what I say.

When improving behaviour, I ensured the involvement of all staff in decisions and policymaking. This meant that they had ownership over the approach being taken and that they were able to apply the policy consistently. When teachers have found this hard, I have worked alongside them, modelling, encouraging and enabling them to see that consistency works.