During one of the sunnier moments of last week, I dragged my gently dozing pupils outside to embrace the crisp winter sun - and enjoy an impromptu geogophysicnumerenglish lesson (a subject I invented myself, for precisely this situation).

Despite all huddling together like a colony of penguins, and periodically complaining about the cold, they began to get into the spirit of things.

I drew a large chalk circle on the ground and told them that it represented the Sun. “So if that’s the Sun,” I explained, offering a stub of chalk to willing participants. “Where do you think the Earth would be?”

Little Andrew stepped forward. He glanced at me cautiously, then crouched on the floor and drew a small circle, several centimetres away from the Sun.

“If the Earth was there,” I replied, “we would all be burnt to a crisp.

Anyone else?”

One of the smart girls took the chalk, and walked confidently to the other end of the playground. “Is it over there, Miss?” “A good guess, but actually, if this really was the Sun,” I said, pointing to the chalk circle, “our Earth would be as far away as the Asda car park.”

“Wow!” came an impressed chorus of voices. I even threw in an extension activity (eat that, Ofsted): “On your way home, children, ask your parents to take you via Asda, so that you find the Earth for yourselves.”

Then they trooped back into the classroom, chatting excitedly about the lesson. Job done.

The following morning I was approac-hed by a nervous looking Andrew.

“What’s up?” I asked. “Miss, I went to Asda like you said, Miss. But when Dad asked them if they had any earth, they told us to try the garden centre.”

There’s always one...

Louisa Leaman is a London teacher