At my girls' grammar school in Liverpool, Calder High, I was rebellious and ill at ease with the formal teaching regime. I was bunking off and going through a period of quite significant bad behaviour.
There was no excuse: I came from a comfortable background and had a very happy childhood. The problem was all the energy within me which needed, but had not found, an outlet.
Things began to change when I was 14 and Calder High merged with Quarry Bank boys' school and another school to become Quarry Bank Comprehensive. Bill Pobjoy, its headteacher, became the most important influence in my life.
He was notoriously liberal. His experience of teaching had shown him that humiliating children was wrong and he became the first head in the country to abandon corporal punishment.
The merger had created a school with a really broad social mix and he was determined to make staff and pupils feel that they couldn't operate any kind of hierarchy. All kinds of intelligence were to be valued. I had moved from a very restrictive regime to one in which you were challenged to behave like a mature human being.
The most important thing about Bill was his incredible politeness: he was always softly-spoken, never manipulative. He treated us all as individuals and we felt respected. If the head is like that, the culture filters down into the whole school, and there was a good atmosphere throughout Quarry Bank. I don't remember any bullying or violence.
When he spoke to me about my bad behaviour, he didn't say "This won't do. You're going to have to pull your socks up." Instead, he said: "I think you're an existentialist and you're testing out the boundaries of reality." I didn't even know what "existentialist" meant but I was so flattered that he thought I was one that it almost reformed me overnight.
At that time I wanted to be an actor and he was the first person who didn't say, "Yes, but what are you really going to do for a living?" I appeared in school plays but felt frustrated at not having a more personal way to express myself. When I explained this he suggested I form a theatre company.
I got together with Clive Barker (the horror writer) and Les Dennis (the comedian), and we did improvisations every lunchtime. Bill watched us from time to time, but even if he didn't like what we were doing, he recognised that our activity was valuable in itself.
When I was 16 and realised that I wanted to direct, Bill sensibly said "You must read drama at university", and convinced me that I had to start working towards the future instead of just enjoying the present.
I didn't start swotting in my bedroom every night, but I did give up some of the extra-curricular things - like singing in folk clubs. There came a point when I was able to have a longer-term view of myself. My parents were full of admiration for the positive influence Bill was having on me.
There were only four universities that offered drama single honours in the early Seventies, so there was huge competition for places. You needed four A-levels, which made it vital that I pass French. Bill, who was an excellent French teacher, gave me private lessons, which undoubtedly got me through the exam. He was really committed to me, but I saw him take just as much care with many other pupils.
I can see Bill's influence in the way I direct. Right from the beginning of rehearsals I try to make actors feel that they are not going to fail - for me, as for Bill, it's a question of how we are going to achieve success, not if.
I can't know for certain if my life would have been different had Bill not been there, but I love what I do so much, and have been so happy since becoming a director at 22, that I can't help thinking about Bill's influence. When I got the OBE last year, he was the first person who rang me - at 8am - to say "well done".
Jude Kelly, OBE, 43, has been artistic director of The West Yorkshire Playhouse in Leeds since 1988. Her first opera production, Donizetti's The Elixir of Love, opened at the Coliseum on January 26, and in April she will direct the world premiere of Ben Elton's Blast from the Past