They must take a memory module at teacher training college. The kind they advertise in the Sunday broadsheets, where a gormless-looking man in a cheap suit makes excruciating social faux pas until he discovers a mail order plan offering total recall in 10 easy payments. How else can the staff in the infants greet each child every morning with a cheery smile and the correct name?

So spare a thought for the parent-helper who does not have the benefit of professional instruction. For I am that gormless man. (Not literally. He must be 80-odd by now. Or at least his suit is.) And please be aware that there are times in the classroom when I may not know which child is which.

Like today. Mrs Lewis asks me to follow up some computer work I did with Archie’s group last week. Archie? I try my best. I know there is an imaginative rhyming procedure where you link faces to names in a vivid mental tableau that you can’t help but remember. Give me a Dan, and I will imagine him in a van eating All-Bran from a can. But Joshuas or Chloes test my powers of poetry. Instead, I make like a quality controller in a ping-pong factory, scanning near identical shiny round faces, checking for flaws. A slightly wonky fringe? An over abundance of freckles? But it’s impossible. This lot could be cloned space-babies from Village Of The Damned, though hopefully without the psychokinesis and plans for world domination.

I try to recall where I sat last week, but there is a free-form ebb and flow to the classroom where children forever dash away for interesting reading exercises, or to plant sunflowers in the courtyard. And there is a free-form ebb and flow to the children. Week by week, they display the sort of dazzling metamorphosis that would usually require a multi-million-dollar special effects budget. Missing teeth. New teeth. Growth spurts.

Time ticks on. I concentrate like I’ve never concentrated before. A snub nose looks familiar. A ponytail rings a bell. By elimination, I narrow Archie’s group down to two possible tables. But I still face the final hurdle. I need to distinguish the small mousy boy called Archie from the small mousy boy called Alfie. OK, one of them is my son, but that just piles on the pressure.

Michael Cook is a freelance copywriter and a parent helper at Ernehale infants school, Arnold, Nottingham, which his children, Alfie and Poppy, attend