It has taken a dairy-based disaster to get me into this department store. Some things look pretty in pink but not the inside of my rucksack, where the friendly bacteria in my strawberry yoghurt have done little to improve the health of 28 pieces of assessed writing and Mrs Watson’s passport application.

I am determined that my new school bag will be an improvement on the last one. I’m looking for something fashionable, functional and less attractive to flies.

“I don’t think this one works, do you?” I say to the shop assistant. She smiles patiently and informs me that these days men tend to wear the messenger bag across the body rather than dangled from one shoulder. I adjust it accordingly as she stifles a fit of giggles. “It’s just that I’m not used to wearing a man bag,” I explain. “Do you have anything for a more mature person?”

I tell her that I’m looking for something that will hold upwards of 30 exercise books, a year’s worth of training handouts, several hundred confiscated Match Attax cards and a packed lunch. “And I’m a primary teacher,” I add, “so don’t even think about one of those overpriced leather satchels.” She consults a senior colleague before returning to tell me she has the perfect thing.

Unfortunately, a briefcase from their extensive and exclusive range is not what I had in mind. It may be good for carrying documents, but it also carries disturbing memories of my first teaching job, 100 years ago. “I have nothing in my teacher wardrobe that will go with a briefcase,” I tell her. “My old corduroys are no more and my jacket with leather elbow patches has been consigned to the jumble sale of history.” She smiles brightly and says, “What about a rucksack?” I return her smile and tell her that I already have one. In fact, it is currently hanging on the washing line at home. And although it fulfils many, if not all, of my requirements, it has one very serious drawback. Lots of students own rucksacks too, and many of them are quite similar in appearance to mine.

I ask the assistant to consider what might happen if a child, having had a serious disagreement over a trivial football-related incident during playtime, were to mistake my rucksack for that of his rival. And what if this resulted in him kicking it all the way down the corridor and across the full width of the playground before lobbing it over a fence?

It seems a shame to make this rare visit to a large department store only to leave empty- handed, so I head three floors down to the basement where they sell various household appliances and kitchen equipment, including storage utensils. Here I purchase a durable plastic lunchbox with a lockable lid and a guarantee that its contents will remain safe, secure and fresh.

“Would you like that in a carrier bag, sir?” says the girl at the till.

“Now why didn’t I think of that?” I reply.

Steve Eddison teaches at Arbourthorne Community Primary School in Sheffield