Please Sir! was set in the fictional Fenn Street School, and starred John Alderton as Bernard Hedges, a young teacher fresh out of training college. The supporting cast included Deryck Guyler, Joan Sanderson and Richard Davies. Character actors and actresses formed the supporting cast, including Mollie Sugden as a parent of a student, Barbara Mitchell as Frankie Abbott's mother, Ann Lancaster as Mrs Rhubarb in a 1968 episode.
Bernard Hedges and the 5C pupils were replaced by a new teacher and pupils for the final series in 1971–72, while the original pupils continued in a spin-off series, The Fenn Street Gang, which ran for 47 episodes between 1971 and 1972. This was followed by Bowler (1973), following crime boss Stanley Bowler, played by George Baker for 13 episodes.
Like many situation comedies of this era, a film version was released in 1971. This was set in an outdoor pursuit centre, but starred most of the TV cast.