Every classroom has at least one, and if I was stranded on a desert island with a class to teach, I would want one too. I’m talking about what can only be described as an object of unclear purpose and origin.

This is another of those teacher experiences that goes back to when I was a pupil. I can remember the squashed ball-shaped object sitting on Miss Bolt’s desk. It was fascinating, alien-looking and I found myself staring at it every time the crocodile of pupils in which I stood wound its way around her desk. Everyone touched it and stroked it as they went past; no one ever picked it up. We would ask her what it was, and she would just reply, “I wonder”, which would bring out a suggestion from someone, followed by murmurs of agreement and shaking of heads in equal measure. It must have been a few years later on a daytrip to Margate that I saw a whole shelf full of these sea urchins. I couldn’t believe there were so many of them, so unique had this object seemed to be.

So I search for objects that are either hard to explain or have no explanation. My most recent additions are a curly metal figure-of-eight thing that keeps railway tracks on their sleepers and something that looks a bit like a Giant’s nit comb but is really a device for holding onions still while you slice them. As objects such as these are passed around, I see pupils mime with them, exploring them with their fingers. I watch as they point out details that are barely visible to the naked eye, yet play a vital part in their own personal theory. As a talking point and a gateway to the imagination, objects such as these are priceless. Just as useful are items which may be instantly recognisable, but are incomplete or out of place. Take a big key into the classroom and see where it takes you. Do the same with a torch, a whistle or old-fashioned pocket watch.

The digital camera can be used to give this a twist. Anyone old enough to remember the quiz show Ask the Family will remember the photos of objects taken from unusual angles. Use the data projector to show a photo taken by zooming right in to the fire extinguisher on the wall, or take a bird’s eye view of a whiteboard pen top. The pupil who guesses correctly could be challenged to take the next photo and so on.

I used to think that my Grandma’s explanation of objects as “neither use nor ornament” was one of the most scathing of put-downs. As a description of objects in my classroom however, I consider it rather a compliment.

Peter Greaves teaches at Dovelands Primary School, Leicester

Email: primary@tes.co.uk