First impressions count, and nowhere more so than the classroom. From the moment your pupils meet you, they have decided what kind of teacher you are - and what kind of class they are going to be. So you need to get it right.

Most guides to behaviour are written like theses for masters’ degrees, which are little use to the average new teacher; you need simple, practical advice to use immediately. So here it is:

It’s YOUR room, not theirs. You’ve heard the saying: “Don’t smile at them until Christmas?” And like every other teacher, you’ll probably ignore it, so keen are you to build up a confident, friendly rapport that nurtures their minds, emotions and chakras.

What are you, Gandhi? You’re in charge. So be in charge. Let’s look at your appearance. It’s cruel, but most children still associate authority with sober, slightly stern dress, so you’re crazy not to tune into this subconscious expectation. Do yourself a favour: close your eyes and imagine what a teacher with great control looks like. Then go to the wardrobe and dress like it.

Be in the classroom before your pupils, preferably at the door. Have every resource you need on your desk before they get there, to avoid the temptation to nip out for glue, scissors or a hankie. If there’s anything pupils need once you’ve started, do without. What they want is secondary to what you want.

As they enter, look everyone directly in the eye and say good morning, at respectable intervals. You are now providing an example for them to imitate. Start by being polite and firm. They deserve the kind of manners that you expect from them. And as they’re entering, let them walk around you; don’t move for them, because you are in charge. If anyone is messing around as they enter, ask them to wait outside, calmly and always politely. They need to learn from the start that you have high expectations. Have work ready for them, on the board or desk preferably. Your name would be good, plus a few simple instructions that everyone can see and understand, along the lines of “coats off, sit down quietly”. This room has rules.

Once they’re in, allow a minute for them to settle, and then introduce yourself. Initially, use less humour than you would at a funeral; they need a teacher, not a laid-back entertainer. They’re crying out for leadership, so give it to them.

Use impact to communicate. You’ve probably heard that we only get across 25 per cent of our message with the words that we use - it’s true, and that means that you’re talking to pupils with more than what you say. Think about how you conduct yourself. Picture that perfect teacher again. Are they racing around, biting their nails and staring at the floor? No, so you’re not either. Stand still. Let your feet grow roots and stay planted in one place. Keep your arm movements small, and make them certain, deliberate gestures. Think the BBC newsreader for carriage, and JFK for gesticulation. Observe other teachers, and imitate their successful non-verbal cues.

Sound like you mean it. When you’re speaking to persuade others, always avoid a) talking like they are worthless (because they’re not), b) talking like you are worthless (because they’ll believe it and use you like a human pinata). Instead aim for c) the assertive tone. Talk to them as if you were asking for something at the supermarket, neither urgent nor wheedling. Requests with presence need neither a question mark nor an exclamation mark at the end, so lay out your needs like a manifesto. Raise your voice as little as possible - I only do it when the class can’t hear me. It can make you sound like you’ve lost control, which may be what some of them are looking for, especially if you have a high pitch.

Be consistent. This is the real key to long-term behaviour management. The pupils will test your boundaries, so have some lines drawn in the sand. Make your behaviour expectations clear from day one; get the rules stuck into their books, and spend the whole first lesson on those rules if you need to. Let them know that you think it’s important, because you need a calm, safe space to help them to learn. Embed your behaviour policy by making them aware that you care about them as learners, even if they don’t.

Let them know what the rules are, and let them know what the sanctions are if they break them. And employ these sanctions when the rules are broken, or all you’re teaching them is that your words are meaningless, and your rules are empty.

Consistent means fair. Don’t pass judgement like Moses one day, then be bashful the next. That just teaches pupils that you’re inconstant. Follow the whole school behaviour policy as much as you can, because that shows them that you aren’t alone, but part of a team - that’s a good lesson for you to learn too.

It’s a marathon, not a sprint. Every new teacher needs to hear this. Many start off well, applying themselves to discipline with nervous gusto, until they feel that things aren’t improving, and they crumble by February into a heap of misery, throwing out all their sanction procedures with their good intentions and self esteem. Who can blame them? It seems at first that the pupils will never like you, and the bad ones are still... well, bad. Phone calls home, detentions, reports, still aren’t working, and it all looks hopeless.

And that is the secret and the problem. It takes time for pupils to get used to your rules, and they will initially resent you for it. But they’re learning, despite appearances. It’s at exactly the point you feel it isn’t working that you need to keep going.

Once you break through the seemingly impenetrable gravity of those initial months, perhaps the first term or two, you achieve escape velocity and fly into orbit. Keep going. Keep every one of your procedures in place. Keep making the phone calls home, keep chasing the detentions, and keep putting the pressure on them, even when you don’t feel like it.

You are the grown up. You are part of a greater team that has their best interests at heart. You are in charge; so act like it, even when on the inside you feel at your weakest. They need you to be the boss. So be the boss.

Four tips for Day One

1. Get a seating plan. You learn their names, They will learn to sit where you tell them.

2. Ignore questions without a hand up. Ignore them completely. They’ll learn.

3. You will feel tempted to be kind, laugh and say friendly things. Resist.

4. Try to avoid saying: “I’ll get MissSir if you don’t behave”. This teaches them that you’re not in charge; MissSir is. Use others as a last resort

Tom Bennett is head of religious studies and philosophy at Raine’s Foundation School in Bethnal Green, east London Next week: Think you’ve got behaviour management cracked? Tom Bennett looks at how to unlearn your bad habits - and how to take classroom control to the next level.