Mr Majeika, Paperback

Mr Majeika can behave just like any ordinary teacher if he wants to, but something has to be done about Hamish Bigmore, the class nuisance, and so he uses a little magic to turn him into a frog. And to everyone's delight it looks as if Hamish will have to remain a frog because Mr Majeika can't remember the spell to turn him back again.