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 Teaching is a highly nuanced, complex art, where the most effective teachers build up a range of strategies over years and years of practice. I opted out of the classroom too early to do that, and moved into what in many ways is a less complex, but equally demanding, role of senior administrator, or leader, in schools.

I taught for about 15 years, and some of that included being a head – in fact, I only had one year as a head when I didn't teach. During those years I am really proud of the impact I had on my students. I admit that I didn't get it right with all of them; one set of parents asked for their child to be removed from my tutor group because I was too hard on him.

I certainly erred on the high-expectations, no-excuses side of the fence, and early on in my career I was too blunt in my approach. I still remember the ignominy of sitting in a room with the parents and the head, listening to the parents complaining about me. The head had warned me to keep quiet, so I wasn't able to defend myself. It was agony.

One child I worked with when he was about 11 seemed to be in a world of his own. Michael talked to himself and had a high, squeaky voice. I can't remember why, but I made him sit right at the front of the class. He huffed and puffed his way through lessons and made it clear that English was not his preferred subject. His handwriting was distressing to look at and if he was asked a question, he would laugh nervously in the hope that I would give up and move on to another pupil.

Once we were studying a complicated poem and I asked him to explain what was going on. I wouldn't leave him alone and he began his squeaking and puffing. I simply said, "Michael, I'm not going to let you off the hook. I know you can do this, so we'll all simply wait for you to explain." After what felt like an age, he eventually expressed – in phrases of exceptional clarity – what the poet was trying to achieve. It was a moment of revelation for the class and for me, and from then on, I never let him get away with anything other than exceptional work.

His parents later invited my wife and me out to a restaurant. I remember it because we had little money at the time and going out to a restaurant was the sort of classy activity we never indulged in. Michael's father said how grateful he and his wife were that I had broken through to Michael in a way that no one else had, and that he was now a different child. I remember feeling embarrassed, and throwing off the praise by way of avoiding an emotional response. But it still strikes me how powerful a teacher can be in unlocking children in a way that reveals – both to them and the world – that they have something worthwhile in them.

I can't think of another profession or role which affords this privilege. Maybe being a parent, but so often children discount the words of their parents (I know my own do). As a head, I would often tell teachers that they had the opportunity of seeing the differences between otherwise similar human beings. What sort of language and phrases and idioms did different children use? Who challenged the way teacher questions were articulated? Which children got bored more easily? Which seemed to cope with higher levels of challenge?

The differences become infinite once you start looking for them. I would ask teachers to point out to children how they were different and how that difference was special. I would get them to tell the parents too; after all, parents usually only have one, two or three other children to compare, and it is tough to describe children on a learning journey except in relative terms to how the others are doing.

It is too easy to describe children's learning in fairly bland terms. I know that many primary teachers have three main descriptors for how children in their class are progressing in each subject and therefore have only three different types of comment when writing reports for parents. That is so reductive as to dismiss the significant opportunity a teacher has to notice difference, and to do so in detail. Bland, generic reporting should be binned, to my mind. Teachers should work with each other to develop much more detailed observations of children and what they are like, in the quest to discover the potential in each child. This, of course, needs to be done in a way that does not bury the teacher in extra work – it's challenging, but possible, and potentially highly impactful.

I was taught languages in a highly structured way that was exceptionally challenging and rigorous. I was taught science in a formulaic (sorry) way that was slow and tedious, meaning I quickly lost concentration. I wasn't genetically indisposed to understanding science – both my parents were doctors – but the teacher treated us as a mass (sorry, again) of pupils, rather than a gathering of individuals. There was little attempt to ensure that every child was keeping up on the journey.

Get it right, and the teacher's role is life-transforming and endlessly exciting. Get it wrong and it is a tedious, repetitive profession full of stress and exhaustion. It's up to the senior leaders to set environments where the former is the norm; it is up to teachers to embrace the potential that they have in their hands.

This article is an adapted chapter from Fergal Roche's new book, Mining for Gold: Stories of Effective Teachers.