When I trained to be a teacher, my first lesson was with a group of 14-year-olds in a temporary classroom apart from the main school buildings. It symbolised to me, in my agitated pre-lesson state, detachment from the authority of the school.
The students had arrived before me and, silhouetted against thin sunshine, I could see that several of them were fighting. I was, I felt, walking knowingly into a lions' den. It was me against them.
The previous week, I had observed a veteran teacher with the same class and marvelled at the way he reined them in to a state of obedient silence without speaking a word. A look was all it seemed to take for the students to become pliable, smiling and eager to learn. It made teaching seem somehow mystical, and most definitely unattainable. I could understand all those people who had told me that being a teacher was a talent you had or didn't have.
I had tried every trick in the book to give myself some superficial authority. I had grown some unconvincing facial hair and dressed in a middle-aged man's sports jacket and brown tie. But I quickly learned that teaching was not quite as mystical as I had thought. I realised that subject knowledge is less important than other stuff: knowing where to stand in a room; knowing how to signal that the territory now belongs to you (changing the lighting and the temperature, insisting that bags be on the floor rather than on desks).
In his collection of essays What the Dog Saw, Malcolm Gladwell quotes an educational researcher, Jacob Kounin, who studied how teachers deal with low-level poor behaviour. The most effective are those who prevent tiny misdemeanours - talking when the teacher is, being distracted - from growing into big misdemeanours.
The really interesting bit of Kounin's research is that it is not really a matter of the teacher knowing how to deal with defiant or aggressive behaviour when it happens; it is about stopping the small stuff from developing into bigger stuff. It is what Kounin calls "withitness".
He defines this as "a teacher's communicating to the children by her actual behavior (rather than by verbally announcing: `I know what's going on') that she knows what the children are doing, or has the proverbial eyes in the back of her head".
I like that: "withitness". It makes sense. It is the way teachers make the classroom their own, model the behaviour they expect from students, use body language, pauses, praise. It is the real stuff of teaching.
And that is why we need to keep the focus on teaching, not endlessly tinker with the structural stuff. The more teachers are expected to implement a new curriculum - the "what" of the classroom - the less time they will spend on the "how". So let's avoid endlessly changing the "what". But to do that we will need our politicians to adopt a form of "withitness".
Geoff Barton is headteacher of King Edward VI School in Bury St Edmunds, England.