I'm notorious among the other maths teachers for using crazy ideas in my lessons. Some of these result in me landing flat on my face on other occasions things work spectacularly well and I feel all dynamic and smug.

On Thursday I was teaching a lesson about speed - as in motion, not drugs, the kids could probably teach me more than I could them about that kind of speed - and was using a remote control car to demonstrate the point. I set up a circuit using textbooks and the kids did time trials around it.

It actually worked rather well, but to an outsider it would have looked terrible: textbooks strewn on the floor, a pupil playing with a toy car, another using his phone (the official timekeeper) and the rest stood around doing nothing much in particular.

No wonder senior management think I'm incompetent.

We gave our year eights an old year nine SATs mental test as part of their exams. This meant there were several questions on the tape that involved work they’d yet to cover, so they had no real way of working out the answers. I told them to take a guess. I’m not sure they really thought it through though as some decided that the circumference of a circle with diameter = 8cm was ‘apple’ or ‘blueberry pie’.

That wasn’t quite what I meant.

I also worry about their general logic skills. There was a question about comparing prices of toilet paper and they were hopeless at it. They were told that a pack of nine rolls cost £3.90 and a pack of six was £2.50. They had to decide which was better value.

So they worked out that the pack of nine was 43p per roll and the pack of six was 42p per roll. Fine so far.

Unfortunately most then decided that the pack of nine was better because it was only two pence more but you got more rolls.

Good grief. Tesco will be rubbing their hands with glee. I can now see my purpose as a maths teacher – it’s so I can stop future generations blowing their money on toilet roll.

Still they were at least more right than the pupil who said that it was better to by the pack of six because you saved £1.40 and you could try to make the rolls last longer.