A millisecond after Ryan walks through the door, an image of his face is imprinted on my retina and transferred to the visual cortex of my brain. One moment and several thousand electrochemical reactions later, a contingency plan is formed. Urgent messages are relayed along neural pathways at speeds of up to 300mph, stimulating muscles to contract and joints to move. Before Ryan can kick his book bag across the floor, shoulder-barge Courtney into the wall and tell Nathan to get out of his face, I am gently ushering him towards the nurture room.
This is where good behaviour management begins: reading students' facial expressions. These signifiers instantly reveal the nature of human emotions. And decoding them is what good teachers spend a lot of their time doing.
Experts describe seven basic emotions linked to particular facial expressions. These are: surprise, fear, disgust, contempt, anger, sadness and happiness. If you manage to pinpoint every one, you will be akin to Tom Cruise in the film Minority Report, able to stop crime before it happens.
But emotions and facial expressions are complex things that seldom appear in their simplest form. To combat this problem, I have come up with four categories of facial expression that I call "the weather forecast". Although this system does not solve behaviour issues, it at least gives me a decent idea of who the culprits or victims may be, and whether to expect problems.
Fun in the sun
Most children come to school with sunny smiles on their faces. Sunny smiles, however, are relative. Some children are naturally more energised than others. For example, opening my classroom door in the morning and finding Cody on the other side of it is like stepping out of a dark cinema into a bright summer afternoon. But Harry's smile is just as valid, even when it is harder to spot than a pinpoint of light in a distant galaxy.
Being greeted with a smile - a genuine smile - is an indication that you are doing something right, and that no one else in the class is doing anything wrong, at least not to the smiler in question. It is a nod of approval, indicating that the behaviour-management outlook is, for the moment, good.
Ryan's face is the weather equivalent of a family holiday we had in Wales in 1972, an endless stream of dark, brooding scowls illuminated by lightning flashes of anger scudding across his countenance.
Stormy-weather faces are the easiest to spot because the danger signs are there for anyone to see. You are going to have issues. My only advice is to batten down the hatches and inform your school's equivalent of the coastguard service that you may be in need of a lifeboat. Take evasive action and hope for the best. You can't pre-charge the student with an offence, but you can ask them what is wrong and keep a very close eye on their actions thereafter.
It is never easy to interpret a facial expression that is doing its best to avoid being interpreted. There are days when making any sort of eye contact with Leanne is like trying to read the use-by date on that three- year-old jar of capers languishing at the back of the fridge.
Faces that appear to be almost perpetually clouded over with ingrained evasiveness, that seldom smile and avoid eye contact at all costs, should be treated with caution. There may be a plan forming, there may be a plan in action, or there may even be a completed plan awaiting discovery. There is not a lot you can do in this situation but wait and brace yourself.
My advice is to expect the worst while remaining hopeful that the gloom will eventually lift and the sun will come out. Alternatively, of course, avoidance can indicate that the student is upset, so it is worth looking at their relationships with other children and perhaps having a quiet word to check that everything is OK.
Chelsea looked like she was frozen in time, a pale orphan from a bleak Victorian winter. Every day she came in late, and she was increasingly tired and unkempt. It would have been easy to ignore this, because she never caused a behaviour problem. Her only crime was to fall asleep in the book corner.
But when a child's face induces a shiver of concern, the matter has to be reported. It didn't take long for us to discover that Chelsea's mum had walked out and her dad was struggling to cope on his own with four young children.
But take care: family problems are not the only reason a child might come to school looking pale and traumatised. Guilt about indiscretions perpetrated, or upset at being the victim of someone else's indiscretions, are just as likely. Ask the student what is bothering them before you act.
This particular facial expression can have another cause, of course. One day, Cody was a pale ghost of his normal self. My concern for his emotional state was immediately aroused, but only until 9.30am. He felt much better after showering the classroom with the contents of his stomach.
Steve Eddison teaches at Arbourthorne Community Primary School in Sheffield, England.