- Actor-Inspired Element: Mick and the Girl rolling on the café floor naked and making love was Malcolm McDowell's idea (because he wanted to see his attractive co-star, Christine Noonan, for whom he admitted having a crush, in the nude.) However, when Lindsay Anderson accepted his star's suggestion, the director required McDowell to ask Noonan if she was willing to do so. (Her reply, according to McDowell, was "I don't mind.")
- Banned in China: The film is noted for its highly controversial content (both at the time of release in 1968 and even in the present), including romance between male pupils, nudity, feral sex-scenes and pupils gunning down their classmates, parents and staff in the surreal finale — the film was X-rated upon its UK release.
- BFI Top 100 British Films: #12.
- Darkhorse Casting: Prior to this, Malcolm McDowell had small roles on the stage. His only prior film role was in Ken Loach's Poor Cow, where he ended up on the cutting room floor.
- Dawson Casting: Played straight with the older pupils, who were mostly in their early to mid-20's at the time of shooting, but the younger First Years (the "Scum") all look to be of the correct age (11-12 years old) for starting secondary school.
- Star-Making Role: For Malcolm McDowell.
- Stillborn Franchise: At the time of Anderson's death he had completed a final draft of a proper sequel to the film, but it was never made. The sequel takes place during a Founders' Day celebration where many of the characters reunite. Mick Travis is now an Oscar-nominated movie star, eschewing England for Hollywood. Wallace is a military major who has lost his arm. Johnny is a clergyman. Rowntree is the Minister of War. In the script Rowntree is kidnapped by a group of anti-war students and saved by Mick and his gang, though not before Mick crucifies Rowntree with a large nail through his palm.
- Throw It In!: The scene of the beating in the gym was completely adlibbed.
- Unintentional Period Piece: Conditions for pupils and staff are rather spartan, but this no longer applies. School fees have been rising faster than inflation since the 1970s, and a lot of the extra money has gone on a "facilities arms race." Private schools nowadays are reported to be very comfortable.
- What Could Have Been: Nicholas Ray was asked to direct. He liked the script, but he suffered a nervous breakdown before anything could come of it.
- Working Title: Crusaders
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