How much does a Jaffa Cake weigh?
Unfortunately, we are long past that stage in our house. We are not so much minor deities as minor inconveniences. It's not that our children have entirely given up on us. That won't happen until the morning of their 13th birthday. But they are already aware that their father has no memory for childish things, such as the names of Harry Potter's schoolmates or how to keep a Tamagotchi alive. And the grown-up skills that once brought me credit (clever Daddy knows a special way to turn off the kitchen tap so it doesn't keep dripping) have been reinterpreted as serious character flaws (stupid Daddy cannot fix the kitchen tap).
Teachers are afforded a little more respect. And in school it seems some teacherly magic has rubbed off on me. The children in this morning's maths lesson expect me to know the answers. We have a tray of household objects and a tray of weights. We must hold a pen, a book, a glue stick and some cakes in one hand, and five, 10 or 50 grams in the other and try to determine how heavy each object is. Then we weigh it on kitchen scales to see if we are right.
The children want me to save them the bother of estimating, and just tell them the answers straight away. It takes me a while to convince them that I am as much in the dark as they are. They are astonished to be told that, off the top of my head, I am not sure of the precise weight of a single Jaffa Cake. They do not believe me when I say that my guess is as good as theirs.
Maybe these children don't in fact consider me the font of all knowledge.
Maybe they have looked at my middle-aged spread and have me down as a man who knows his way round a biscuit barrel. But I think they assume that grown-ups just know this stuff. All stuff. Any stuff. Even after I've pointed out that the only person likely to memorise the weight of a Jaffa Cake is the quality control manager at McVitie's.
They would realise just how wrong they were if they saw me at break time.
When Mrs Todd goes off to get us both a cuppa, I dig some bathroom scales from the cupboard. The speed that I jump off them, and the expression of shocked horror on my fat face should be proof enough that, when estimating the weight of something, I might tend to err a little on the low side.
Nevertheless, I eat a Jaffa Cake with my cup of tea. They don't weigh much, after all.
Michael Cook is a freelance writer and parent-helper at Jesse Gray primary school, West Bridgford, Nottingham, which his children Alfie and Poppy attend