The plan was for 30 children to work in pairs at a computer. I should have checked beforehand as, upon arrival at the classroom, I discovered that only 10 machines were working.
The inspector was a vast woman who sat hunched, frog-like, scribbling notes on her pad. I got the children to sit on the carpet, buying me some essential thought time. The first part of the lesson went well: some of the children helped me input data from the school surveys we had done previously and we managed to get the temperamental printer to produce a beautiful graph.
However, we then came to the part of the lesson that required pair work on the computers. Utter chaos erupted as 30 children scrabbled for the machines that worked.
Horrified, I looked to the inspector, planning to placate her with a broad smile. Miraculously, I saw that she was sound asleep on her chair. I quickly improvised and got some broken keyboards out of the cupboard. I put them on the carpet and told a group to work on their typing skills.
The inspector eventually awoke, but only as we were leaving the room. She stood, patted me on the shoulder and said: "That was excellent, thank you."
I learnt a great deal about preparation that day and also that boiling, stifling classrooms can have positive uses.
Worst: It was optional Sats time. It was pouring with rain and the hall and ICT suite were out of action. It was only a matter of time until my rebellious Year 5 group made me pay. I somehow managed to navigate the first class of the morning without too much difficulty. However, at 10.30am I had to tell them that it was wet play. The result, unsurprisingly, was a massive explosion of tempers and angst.
Three children climbed on the table, one swung on the door frame and shouted obscenities down the corridor; two boys broke into the ICT suite and began disassembling the computers. But this was the least of my worries as a huge fight suddenly broke out over something small and insignificant.
I intercepted the brawl, pushing myself between two snarling children only to hear the words: "Sir, catch this" as a metal chair came flying through the air towards me.
I jumped up; the other children froze with astonishment as I grabbed the hurtling chair by one leg with one hand. At that moment, I noticed that the headteacher was standing at the doorway with some prospective parents, mouths agape. Complete silence fell over the classroom. I seemed only capable of making a gargling noise.
There was no way out, until one of the perpetrators said: "We're revising gravity."
Robin Warren is headteacher at Moss Hall Infant School in Finchley, London.