There are many aspects of the infant teacher’s role that other highly educated professionals rarely encounter. There are few chartered accountants who combine an understanding of cash-flow and tax dodges with regular pauses to go round the office wiping noses. A GP has a vast knowledge of disease, unease and the human condition, but is seldom required to turn the surgery into a moonbase armed only with tin-foil and a staple gun.

But there is one part of the primary teacher’s job that must be unique.

When Martin Scorsese is casting a film, it’s up to him to choose the best.

And once he’s called up De Niro or Day-Lewis, he is not expected to fill up the rest of the cast with deadbeats who failed the audition for Hollyoaks.

Yet when Miss Cox opens the doors to Class Six, she is asked to cope with everyone from the brightest star to the dullest cloud - in one class. She can’t cherry-pick the alert and the capable. And quite right, too. The alert and the capable are doing just fine, thank you. What about the rest of us?

Until you experience it first-hand, it’s hard to grasp just how large this gap in ability is. Take this morning: I am working with a bright boy who needs stretching. His mental maths abilities are astounding for a six-year-old - and possibly for an eight-year-old (numbers were never my thing). So we work on problems that test his reasoning abilities as much as his sums. Frighteningly, this doesn’t faze him at all, and he immediately latches onto the nub of the problem while I’m trying surreptitiously to look up the answers in the back of the book. And, yes, he sees through that as well.

Meanwhile, at the other side of the classroom, two children are struggling with number work that my charge was presumably doing in his cradle.

Listening in, you might assume they were doing the same task. I can hear them giving similar answers to my lad, though with a little more uncertainty in their voices. “Is it 20?” “Four?” But draw closer, and you see they are trying to recognise those numbers, written down on the page.

I’ve never been a maths genius. Or a maths dunce. (“Dunce” may not be quite the educational term I’m after - sorry.) But I did learn to swim late in life, when Alfie threatened to rid himself of his arm-bands before I had.

“I can’t understand how you can’t even float,” said a less-than-helpful friend once. “A piece of wood can float.” Mathematically speaking, the infant teacher is asked to teach those who are striving to be Olympic breast-stroke champions, and those who would be happy to be floating pieces of wood. That can’t be easy. And guess what? Tomorrow they go swimming.

Michael Cook is a freelance copywriter and a parent-helper at Ernehale infants school, Arnold, Nottingham, which his children, Alfie and Poppy, attend