A song on Morrissey's first album entitled "Late Night Maudlin Street" is named after the school in this film.
During the filming, Charles Hawtrey's mother would often visit the set. While enjoying a cigarette, she accidentally dropped lit ash from the cigarette into her handbag. Joan Sims who was the first to spot the incident yelled, "Charlie Charlie, your mother's bag is on fire!". Charles Hawtrey poured his cup of tea into the bag, snapped it shut, and carried on.
One of the boys is 17 year old Larry Dann. He would reappear 16 years later in the last 3 official Carry On films (Carry on Behind, Carry on England & Carry on Emmannuelle) playing much bigger roles.
The "children" in the movie are meant to be the equivalent of 6-8 graders, but actually they are played by young adults. This was no mistake - the producers wanted to avoid having to ask the children's mothers for a fee for their appearance as required under Britain's child labour laws.