I was in the middle of explaining some quite difficult work on indices to my year tens. They were focused and keen to learn and I was trying my best to get it across, making sure I was patient if they struggled.

Suddenly the door swings open and in comes the Head of Science with a boy from my form behind him. Why had he dragged this boy to see me? Had he tried to singe a girl's hair with a bunsen burner? Had he called his teacher a wanker? Had he blown up a science lab? If so then I'd certainly want to know, but there's a time and a place. We even have a system of PINs (Pupil Information Notes) to inform tutors of any misdemeanors. However it was none of these things:

'Do you know this boy?'

Well, yes of course I did. I would imagine the Head of Science was intelligent enough to ask the child whose form he was in rather than taking him round every classroom in turn until he found his tutor.

'He hasn't go a pen, I thought I'd bring him up here to save writing a PIN.'

At this point I look around the room for a hidden camera, wondering if this was some sort of set-up. No one jumps out from underneath a desk. None of my pupils zip back their skin to reveal themselves as TV presenters. It genuinely was a case of someone interupting my lesson to tell me that someone in my form hasn't got a pen.

I am then left in peace to get on with teaching a class who looked as bemused as I did.