I wasn't a fan of school, to be honest. I went to the Vale of Leven Academy in West Dunbartonshire, Scotland, between the ages of 12 and 16, and I never felt that I fitted in. I had a tough time, in fact. I was bullied throughout secondary school and for the most part I just wanted out.
But it wasn't all bad. There was one member of staff who had a lasting impact on me: my maths teacher Professor Gillespie. He was about 6ft 5in, a massive man, and he wore a black cape. He looked like a giant crow walking through the corridors. Everybody took the piss out of him behind his back but he demanded authority. It was all "Oh shit, Gillespie's coming" as he approached and then piss-taking once he'd gone.
In class, he handed me a maths problem and I might as well have been looking at Japanese. I remember thinking, "What the hell is this?" At times like that I went into prickly sweats. I wanted to do my best, I wanted to do well, but I had no idea what I was looking at. I read it and read it and read it and got no closer to having a clue how to tackle it.
Professor Gillespie came over, sat down beside me and broke it down into sections. "First section, here's how you do it. Make your notes on that. Got it? Next section, here's how. Bang. Finally, last section. With me? Great." You know how you learn clutch control, and when it clicks into place everything else slots in around it? I just got it. When Professor Gillespie broke it down bit by bit, I got it.
It's no exaggeration to say that I have used that method throughout my life, and not just in maths. As an adult, when anything comes along that seems like a problem, I use that exact method to break it down and tackle it. This guy changed how my brain worked for the better.
Before this interview, I had a think about Professor Gillespie and it struck me how much I use what he taught me, how much I owe him. I'm more organised because of him. If I'm going on tour and my daughter needs elements of her school life sorted, I can sit down and apply what I learned to do that.
I said that he was authoritarian and he was, but he could be kind and gentle when he knew that was the approach needed. He was a fair man. If he thought you weren't working to the level you should be, he would be on your case. I'd love to know if he's still alive, I really would.
And I got my O level in maths, by the way.
Sharleen Spiteri was talking to Tom Cullen. Texas' album The Conversation and the single Dry Your Eyes are out now
IN HER LIFETIME
Born: 7 November 1967, Bellshill, North Lanarkshire, Scotland
Education: Vale of Leven Academy, Alexandria, West Dunbartonshire
Career: Songwriter and lead singer of pop-rock band Texas.