I had a disturbing experience yesterday when I met a former pupil. I bumped into him and shook his hand and asked him how he was doing. He told me he was doing alright and was about to go off to college after a few years in a labourere's position. I usually enjoy meeting former pupils but he then shook me by saying that I had thrown him out of school in fifth year and told him he was an under achiever and would never amount to anything.

I was shocked on two counts – firstly, I don't think that would ever call anyone an underachiever (in a derogatory manner), and secondly I would never have said that anyone would never amount to anything after leaving school. I'm confident I didn't say these things, as these were terms that were said to me when I was at school – and I remember the impact they had upon me. I also think you are tempting fate to suggest that any pupil is the fully formed person they will become when they leave school and so to judge how they might do outside school is folly to say the least.

Nevertheless, he was adamant that these were the exact words that I had used. It was true that I could recall having asked him to leave school – although I can't remember the detail. What it does make me understand is that when you are giving people bad news it's important that you take time to ensure that they fully understand the reasons for the message and that you are careful about the exact words you use. Maybe I had used the words that he was underachieving (which he might have interpreted as him being an underachiever) and that he might have been better to leave school. He did say that I had said that his career aspirations were unrealistic in terms of his qualifications – and perhaps I did.

Anyway I apologised to him and have subsequently wondered how many other people there might be out there who have memories of me as a teacher and head teacher which don't match with my own perceptions. I've always tried to treat people the same way that would like to have been treated. I'd obviously failed on that occasion. On the other hand if this person can use that negative memory as a motivation to prove me wrong and improve his life then perhaps it can still have some benefit.