The pupils you remember most are the ones who challenge you in some way.
Not necessarily in a confrontational sense, but the ones who challenge you as a teacher, the ones who make you think, who stretch your mind and your imagination.
That's certainly why I remember Rachel. She was already in the sixth form when I first taught her - in my A-level English group. One of the set books was Henry IV Part One. We were discussing Harry Hotspur, and I realised that she saw him in a completely different light from me. I had painted him as egotistical, too concerned with martial honour; what mattered to her was that he was youthful and idealistic. On reflection, she was right.
Another time we were reading TS Eliot, talking about that marvellous line, "the burnt out ends of smoky days". Out of the blue, she turned to me and said: "You should read Charles Bukowski."
"Charles who?" I asked. She repeated the name, so I went away and read Post Office and Factotum. I didn't like them much, but that doesn't matter. She had made me think.
It was the same with Thackeray. She enjoyed Vanity Fair, and clearly shared my enthusiasm for the good-humoured feistiness of Becky Sharp. "But shouldn't we be reading Iain Banks as well?"
So I read The Wasp Factory. It was too black for me. "What is it you're telling me?" I asked her. Then I realised it was about being open to literature. Stop reading just the classics and the Booker nominations. Find out for yourself what you like.
It's an odd thing for a student to say to her teacher, but it's something I respected and admired. "Listen to the people you are teaching," she was saying. "Be open to what they feel." In the nicest way, I was learning a lesson about literature. But it was more than that. It was a lesson about teaching, too.
Rachel did her A-levels and went to on to read English at university. She wrote to me once or twice from college. The correspondence faded. But I can see now that there was something of Hotspur in her, and perhaps of Becky Sharp. It's a combination you wouldn't easily forget.
Chris Ramsay is head of sixth form at King Edward VI school, Morpeth, where he has taught since 1979. Do you have special memories of unforgettable pupils? Write to Sarah Bayliss at the address on page 3 or email firstname.lastname@example.org