It's often in the least likely circumstances that we discover astonishing things about others, and possibly ourselves.

One day while teaching I saw Maryanne, a 14 year-old pupil, walk past my room. I asked her what she was doing out of her lesson.

"My teacher said I can do research on my own for a while."

"In other words, you've been thrown out of the classroom."

"Well," she said,"Technically, yes."

Before I could respond to this comment (of which any spin doctor would be proud), Maryanne demanded to know who I was teaching (12 year-olds), and what I was teaching them (spreadsheets).

She asked me to let her help me, and when I replied that I didn't see why I should let her disrupt my lesson as well as her teacher's, she begged me to give her a chance.

I relented, and told her to explain things to the younger pupils, but not do it for them.

I have to say, she was brilliant. She had a great way with the youngsters, and the high degree of impatience she always displayed to both adults and peers was nowhere to be seen. Her explanations were excellent too, and until then I hadn't realised the full extent of her grasp of conditional formulae and absolute cell references.

I've experimented with having pupils in the role of teachers several times, always with great sucess. What made this particular occasion special was that it exemplified something I think we all know: that if you give someone responsibility and have high expectations of them, more often than not they will step up to the plate and not let you down.

Maryanne was always getting into trouble because of her "attitude." But given the chance, she excelled. I wonder if, perhaps, she didn't surprise herself as well.