An HMI arrived unannounced in a biology classroom while it was being used for registration in a west of Scotland secondary and took a seat at the back. She sat through the period and left without comment.

Shortly after the heidie rushed in to speak to the biology teacher and asked about a “totally inappropriate” word on the blackboard.

“What word?” asked the bemused biology teacher.

“Gonads.” the heidie replied.

The teacher’s explanation that the word referred to the animal organs in which gametes, haploid reproductive cells which can undergo fertilisation such as are produced in testes or ovaries, was lost on the affronted heidie who displayed a sense of humour as deficient as his knowledge of biology.

When the teacher told his story in the staffroom, another science teacher immediately headed for her lab, commenting: “I have penis and vagina on my blackboard and there’s sperm on the head of department’s board.”