I was not the most contented of schoolboys. I wasn't really a rebel. I guess I was just one of those generally disgruntled pupils.
Some teachers completely changed that for me. I was always more motivated by the carrot than the stick approach - it probably appealed to my vanity. But the teachers I liked all spotted something in me and I raised my game as a result.
Christopher Pines taught at my primary school, The Dean in Alresford in Hampshire. I was 10 years old and Chris must have been in his 20s. Like all my best teachers he was funny; that mattered terribly to me.
He was incredibly approachable. He maintained discipline through wit rather than any sort of rod or threat of detention. I was quite porous to new ideas at that age. He taught, and I soaked up, everything to do with grammar, writing, dinosaurs and the prehistoric age.
We had corporal punishment at the school: usually a whack on the hand with a ruler or cane. I remember in one art class Chris was cutting paper at the front and he called me up because I talked too much.
He told me to hold out my hand and I thought, "This isn't like him." I was really quite scared for a moment. I held out my hand and he told me to hold out the other one as well. He then put a bin bag in my hands and poured his rubbish in.
He was subverting what other teachers did. Others ruled with threats, but he was the most humorous, sweet and humble man. He went on to become mayor of Winchester.
He used to frequent one of the local pubs and I would visit him there in my late teens. He was always very entertaining . unusual company, and we used to have long chats late into the night.
The last time I saw him was about three years ago. He can be quite critical of what I have done over my career. If he is pleased with one of my roles, the most he will say is, "About time" with a wry smile.
Angela Kirby was another wonderful teacher, who died a long time ago. She taught me O-level English language at Montgomery of Alamein School in Winchester. By the time I got to secondary school I had lost any academic interest. I simply didn't like the curriculum. I would read and listen to things that I was interested in, which was rarely what was on the syllabus.
But in English, there was some overlap. A dwindling bunch of teachers, including Ms Kirby, thought I was clever. I ended up getting an A in English.
Like Chris Pines, she was a creature of the theatre. She had quite a camp, wicked wit, with a shock of bright white hair and flowing velvet dresses. She didn't suffer fools gladly and would use humour and gentle teasing on us pupils.
It was strange to fancy her - she must have been at least 50 and she was no beauty - but we all did. I think it was her friskiness and sophistication we liked.
I remember my form teacher saying that the best I could hope for was to work in a shoe shop. Most of the teachers thought I was a lost cause and were utterly scornful of the whole acting idea. But Angela said that she thought I was university material.
I don't blame the teachers for not thinking much of me. I exuded a lack of respect for most of them. I tended to only respect people if they respected me. I just thought it was common decency.
The teachers who excited me were bright, curious, keen communicators. I had nothing to offer until I was ignited. These teachers made me raise my game - not through force but through sheer strength of character.
Colin Firth is taking part in `The People Speak', a series of live performances and readings about key moments in British history, broadcast on the History Channel on Sunday. He was talking to Hannah Frankel.