At prep school, and then in my first three years as a boarder at Westminster, I was a bad student - recalcitrant, rebellious and constantly playing the fool. The only interest I had in rules was breaking them. My poor parents tore their hair out over my bad reports and the endless complaints from teachers. Only by cramming like mad did I get into Westminster at all.
But just after my O-levels, a young and dynamic English teacher called John Field joined the staff. Suddenly I saw a point to being at school. He was fantastically bright and articulate, adored his subject and shared his love of language with us.
When people talk about actors having "presence" or "charisma", they're talking about energy - and John Field had it. You could walk into his classroom feeling bored, tired or irritated and within five minutes his energy had grabbed you.
If you had seen him walking down the street - tall, elegant and light of foot - you'd have thought he was a head-in-the-clouds type. But his appreciation of literature was the opposite - very earthy. He gave himself to the lessons and if any of the boys played up and abused his enthusiasm he would get extremely angry.
He revealed to us the seamless connection between style and content. He would show you the technical brilliance of dramatic or poetic writing, but never in a dry way, always linking technique to what the texts were about, so we felt we weren't just studying books, but life. The importance of that stylecontent link has stayed with me in my work as a director.
We had no pastoral contact with him. He knew us well, though, and I think he took in more about us as individuals than we probably realised.
The teacher-actor analogy works well in his case. I imagine teachers and actors must have similar crises - "My God I'm talking about Tess of the D'Urbervilles again or "God, I'm performing in Romeo and Juliet again. They always have an audience to satisfy and the best don't just regurgitate, they live off the moment.
I remember studying Tess, Howards End, and a fair amount of Shakespeare. At that stage I wanted to be an actor, and appeared in some of the plays John Field directed. I was Antonio in The Tempest (Stephen Poliakoff, the playwright, was Gonzalo). He brought the same energy to his directing as his teaching; but it would be a lie to say I can see any direct influence from him in the way I handle actors.
Despite my new-found enthusiasm for English, I still suffered a bit of an inferiority complex. The kids who go to Westminster are often ferociously, intimidatingly bright. John Field never made me feel inferior, and his fair comments on my essays were a great tonic. It gave me great pleasure that I got an A in English.
Before starting A-levels I had cast myself in the role of the boy who makes all the others laugh and lives to play football, or party. Suddenly I was taking things seriously. It was no coincidence that I became captain of football and a monitor - positions of responsibility given because other teachers saw the change in my personality inspired by John Field.
My father, Richard, who had not yet started directing films, was determined I should not follow the route he had taken - straight to RADA without a degree. So he also owes a lot to John Field for turning me around so that when I left school Dad was able to persaude me to go to university. I read English at Sussex, directed loads of plays, became president of the drama society and that was that as far as my career was concerned.
I've talked to many people who were at Westminster after me who say John was their favourite teacher, too. A couple of years ago, when I heard he had retired and moved north, I wrote him a long letter explaining what he had done for me, and he wrote a terribly sweet letter back. If he hadn't sparked my interest in literature, I don't believe I'd be working in the theatre now.
If you direct Romeo and Juliet in Stratford, 14 national newspaper critics tell you what they think of you, but how often are teachers told by someone they knew only as a child what a difference they made. Other than my parents, John Field's influence on my development - the creation of my personality - was head and shoulders above anyone else's. He changed my life.
Michael Attenborough, 47, theatre director, was artistic director of the Hampstead Theatre from 1984 to 1989 and is now principal associate director of the Royal Shakespeare Company. His credits include 'The Changeling' and the acclaimed world premiere of Peter Whelan's 'The Herbal Bed'. His production of 'A Month in the Country' is running in Stratford-upon-Avon and will tour England extensively this year. He was talking to Daniel Rosenthal.