Let me say at the outset that my staff are marvellous. They’re hard-working, humorous, never off sick, and committed to their job: a real pleasure to work with.

But they don’t wash their cups. The staffroom has a huge Butler sink, there’s no shortage of water, and years ago the cups would be washed and lined up neatly on the table beside the sink. But in those days, washing the cups was a “primary helper” job, and helpers have now become classroom assistants. They no longer have to wash cups, so the cups sit in the sink.

When the problem first appeared, my trusty deputy wrote a notice saying “Please Wash Your Cup” and stood it at the back of the Butler, but the only thing that got wet was the notice. In no time at all, you couldn’t read it. So she made another and tacky-backed it. The hot water curled it up.

I put a polite note in the staff noticebook asking if people would be kind enough to wash their own cups. Nobody else’s. Just their own. Just the one. But still the Butler bulged.

And then the problem suddenly broadened. A leaving teacher bought a set of cutlery for the staffroom. It didn’t stay there long; teachers would hurry in at lunchtime, fetch what they intended to eat, and wander off to mark books with one hand and eat with the other, taking the plate and utensils with them. Most plates were usually retrieved, some from the oddest places. I found one on the window ledge in the toilet, which, if nothing else, goes to show what busy people teachers are. But where do I find the remaining plates? With the knives and forks in the Butler.

Then one morning I found the sink bleached and the crockery stacked and sparkling beside it. I thought new leaves had been well and truly turned. But no, the cleaner had looked at the state of the Butler every evening, couldn’t stand the pile of unwashed crockery, and worked her way through the lot. Undoubtedly, I thought, the staff will be impressed and feel guilty. Two days later, I realised my optimism knew no bounds.

Once again I put hints in the noticebook. Eventually I ran out of subtle quips; and the Butler ran out of space. My deputy sighed despairingly and set to work after school. I suggested we buy 25 white mugs and write people’s names on them. Then we’d catch the culprits. She pointed out, gently, that people would just use somebody else’s.

We agreed it should become a major agenda item at the next staff meeting. Performance management would have to stand aside while we debated this burning issue. Nobody, of course, owned up to not washing their cups, but there was a wide variety of alternative ideas. A dishwasher, someone suggested. Good idea, I said. The only problem is that somebody needs to stack it. And unstack it. And add rinsing fluid, and salt. Washing your cup isn’t a gargantuan task, I said, just a target. Smart, and achievable. Could we try once again? We agreed we could.

I’m writing this a few weeks into the new term. And I’m just off to empty the Butler...

Mike Kent is head of Comber Grove primary, London borough of Southwark. Email: mikejkent@aol.com.