“Eureka!” I cry, running out of my office, holding a clutch of letters in my woollen mitten as I head to my leadership meeting. 

“I’ve been watching Gavin Williamson’s latest interview - the one about extending the school day or cutting summer holidays - and I’ve finally solved the riddle of the school’s R number.” 

I skip into the staffroom, where my leadership team are sitting a respectful two metres from each other, waiting for our meeting to begin. Their faces are grey and their lips are turning blue, since - despite the central heating being on full blast - all the windows are fully open and it’s bloody freezing. No one is going to get Covid, but we’re all going to catch pneumonia.

“I’ve done it,” I cry again. “I’ve calculated the school’s R number.”

“But the R number isn’t logical,” protests my very logical maths leader, huddled over a steaming cup of Cup a Soup. “R is a letter, not a number.”

“Yes,” I reply, wishing I’d put on an extra layer, and possibly skis. “But nothing the government does is logical. I’ve discovered that it’s based on a simple algorithm that even I can understand.”

Covid: The teacher resignation rate

I grab a pen and start to scribble down the solution on a piece of paper.

“If we say ‘GW’ represents the secretary of state for education,” I explain, giving my best Carol Vorderman impression, “and then multiply this by the number of his speeches, and call this ‘S’, it gives us this solution: the school’s R number.”

I finish writing “GW x S = R” with a triumphant flourish, and hold up the paper for them to see.

My Sendco raises an eyebrow, which is just visible underneath the Cossack hat she’s wearing to keep out the chill. I recognise this as a sign that I need to differentiate a bit, so I add an additional visual scaffold.

Next to the formula, I draw a thin man holding a tarantula, with a speech bubble coming out of his mouth with the word “nonsense” inside it. An arrow leads from this to a picture of an envelope and the outline of an empty school. To the casual observer, it looks like the tormented sketchings of a mad man. I’m hopeless at Pictionary.

“Is it Indiana and Jones and the Temple of Doom?” says my excited early years lead, who has been slightly distracted by her attempts to erect a wind break between the fire exit and the fridge.

“It’s not a charade,” I say (although the dictionary definition of a charade is “an absurd pretence intended to create a respectable appearance”, so I guess it is in a way).

“Just remind me,” pipes up my deputy, her breath coming out in waves of steam, despite the three scarves and two coats, “what is R representing here?”

I stare at her, perplexed. “Isn’t it obvious?”

As one, my leadership team shake their heads, the ice on their collective shoulders crunching noisily as they do so.

Gavin Williamson x speeches = resignations

“R represents resignations,” I cry, waving the clutch of letters still clasped in my frozen hand. “Don’t you see? Every time Gavin Williamson announces anything, the number of resignations goes up. GW x S = R.”

I straighten out first my frostbitten fingers, and then the first of the creased-up clutch of letters I am holding in my hand.

“This resignation is the result of the pay freeze,” I say, putting the letter down on the staffroom table beside a dozen bars of Kendal mint cake. “And this one,” placing the second one beside the first, “is about not moving us up the queue for the vaccine.” 

I place the final two letters beside the others on the table. “Here’s another about not having a phased reopening of schools. And this last one is because of the possible shortened holidays and lengthening of the school day.”

I put a bar of Kendal mint cake on top of the letters to stop them blowing away in the icy draft, and look at my colleagues for a reaction.

There is a stunned silence, and for a moment I wonder if they’ve all actually frozen solid. 

Finally, they exchange glances, reach inside their gloves and produce their own letters, which they pin down with the remaining bars of mint cake.

A freezing blast of air blows in from the playground, and the piece of paper with “GW x S = R” written on it whips up from the desk and straight into my face. I grab it and stare down at the blank side of the paper presented before me.

“OK, OK,” I say eventually, as a chilly ill-wind rushes through schools across the country. “Has one of you got a pen?”

Colin Dowland is a primary headteacher in North London. He tweets as @colindowland