The idea is always seductive: the values of trade are brisk, profitable and fairly predictable. Bums on seats and full order books mean dividends and bonuses. New ideas can be tried. Failures can be written off to experience without much heart-searching. When it comes to raw materials, unreliable or sub-standard suppliers can be berated, nagged, hammered with penalty clauses and blacklisted in the future if they keep sending shoddy stuff.

Schools, however, meet a few snags not experienced by businesses. One year’s botch-ups cannot be cancelled out by next year’s successes: they live on to rebuke you, and their failure resonates down future decades in human failure and unhappiness.

Quality control and estimates of performance are wildly difficult, because every product is an individual. The benchmarks of success - as provided by exam boards - are themselves suspect and are crude tools at the best of times. Much success is hidden, not to surface until years after the product has left the production line, and emerges triumphant in some distant field of endeavour, saying in interviews: “It was Mr Thrumbleton, my history teacher, who first got me going.” But above all, unless you’re a selective independent school of the most hawkish variety, you simply don’t have any proper control over suppliers of your raw material: children.

Instead of a stream of reliable goods, you have a crazily diverse rag-bag of families. They randomly send you these untested children, none of them properly standardised or quality-controlled, many of them with bits missing or dangerous sharp corners. You have to keep adjusting your own assembly line and processing systems to accommodate whatever turns up. It must be maddening. It is enough to make anybody give up trying to operate like a nice modern business and go back to the fusty, old-fashioned idea that a school is a community and children are individuals. Which would never do, would it?

Still, it set me thinking about what sort of ideal raw product a primary school would specify if it had the chance. We are bombarded with surveys about the effect of the first four or five years in a child’s life - nurseries good, nurseries bad, the importance of reading stories, of rough play with fathers and so on. But what, I wonder, truly gladdens a reception teacher’s heart when it rolls off the family production line and is left in the loading-bay of St Crumb’s county primary? You will undoubtedly tell me, but here are some guesses.

The obvious baseline is the traditional advice to parents: make sure the little bleeder knows how to get its shoes on and off, manage knickers in the lavatory and blow its nose. The failure of suppliers to attend to these details wastes hours of worker time at the chalkface. But beyond those basics, it is tricky.

Nursery schools pride themselves on delivering to primary school a steady supply of children pre-loaded with a comprehensive ability to recognise letters and numbers and paste wonky shapes on to paper plates. But hang on: suppose they are too good at it, and the rest of the class isn’t? My own daughter pitched up at Year 1 with a stern and unforgiving outlook: asked to do cutting and sticking in the early days, she said beadily: “I’ve done that, I’m bored with it.” Heaven knows what mayhem she would have caused if she was also tired of sorting, weighing, numbers and the first six books of Roger Red-Hat. There are presumably limits to a reception class’s ability to absorb small, demanding boffins.

Emotional security is definitely a plus point, so perhaps the tot need not have been in nursery at all, but might have hung out with a bright keen parent and a lot of storybooks. Remote hill-farm children, I am told, are often a joy to teach, as well as having an encyclopaedic knowledge of lambing to entertain the class with. But fruity language might be a problem.

The other thing to consider when ordering your supply of perfect children is the sort of parent they drag behind them. The theory is that middle-class parents are “good” for a school, and they are damn useful when it comes to fundraising and hauling in favours. But how good are they for teachers? Is a bright, focused, pre-educated five-year-old worth the hassle of an overbright, overfocused, educationally hawkish mummy who will be outside the school gate every day with pursed lips and a desktop-published list of demands to stretch her offspring’s precious mind?

I dunno. You tell me. What’s the best favour a parent can do for a future reception teacher?

Reply to Libby Purves by email: letters@tes.co.uk