At my last school, one of my tutor group, Liz, was withdrawn and on the social services’ “at risk” register. I made a point of always saying hello. Sometimes I gently ribbed her for having her shirt out or for being late to registration. At my final parents’ evening, her mother told me Liz would miss me enormously - would, in effect, miss terribly being said hello to or nagged.

Liz was one of those children for whom school is not a place where you meet friends because, even though you are a perfectly amiable human being, you lack that indefinable quality that makes your peers happy to be identified with you. Unless teachers talk to pupils like Liz, there is a real danger they will go all day without being spoken to.

So when I make a point of standing at my door as classes enter and leave, it is not just because my headteacher tells me to keep one eye on my room and the other on the corridor - it is, above all, to greet and say goodbye to pupils, with, if possible, extra comments for individuals.

One pupil I tried hard to do this with was Reena. Reena had special needs and spoke in barely a whisper. Finding other pupils prepared to work with her was a daily challenge. I always tried to include encouraging comments in her exercise book. By our third term together, her hand would even go up timidly as she prepared to answer the occasional question.

On my last day, she was hovering nervously outside my oom at lunchtime. When I opened the door, she said nothing but pushed a box of chocolates towards me. I could have cried. I had offered her a few hundred words during our time together, most of them being “good”, “morning”, “well” and “done”, but these words had secured for me a small place in Reena’s heart.

It seems patronising to remind secondary colleagues to acknowledge all pupils, but the chocolates are a reminder that the potentially huge anonymity of the secondary means it can take very little to make a young person feel special.

I understand that Tim Brighouse, Birmingham’s chief education officer, insists that five pupils be designated to each member of staff , who must, each day, go out of his or her way to root out those pupils at break or lunchtime, and talk to them.

Back to the present day. One month into a new post and one month after I first said hello to Charlotte stumbling down the corridor, it is Jeans for Genes day. For the first time in my new school, I see my charges in their own clothes.

I ask a question. Hands go up. I ask the girl near the window and do a double take as I check my seating plan for her name. Despite having recognised her down empty corridors for the past four weeks, I suddenly realise that Charlotte has been in my class all this time, her uniform in a sea of 33 others no doubt contributing to her invisibility. I pray that she never realises I had no idea I was her subject teacher. And though I feel terrible, I at least take consolation from the fact that I had greeted her in the corridor these past few weeks.

Holly Budd is a pseudonym. The author is a head of department and has changed pupils’ names