He saw it as a harmless joke, and one based upon Adrian Mole's obsession with the size of his male organ. The religious studies class had been studying the Mole diaries.
A local councillor raised the matter, however, and Mr Palmer was reported to the police.
He was forced to take study leave after the incident and found himself the focus of media attention. He has now been reinstated but will have a psychologist assessing his next 10 lessons.
"A lot of people have been disappointed to find out how small the thing is. Everyone was expecting at least six inches," said Mr Palmer, who has a reputation as something of a practical joker.
The penis in question was attached to a pair of boxer shorts . . . known as elephant shorts. It was only an inch long, but it expanded to something resembling lifelike proportions when dropped in water.
"It was based on Adrian Mole," said Mr Palmer, who moved to Norway from Cumbria 16 years ago. "He is always measuring the size of his vital statistics and keeps a graph of it. I saw this toy on sale in Aberdeen during a visit and thought I would take a chance. It was all meant as a joke and the pupils took it that way."