Continuity mistake: In the climatic confrontation between Artie West and Mr. Dadier at the end of the movie, West cuts Dadier in the hand with his knife. The scene cuts to Dadier holding up his hand, and it's already covered in blood.
Blackboard Jungle (1955)
1 continuity mistake - chronological order
Directed by: Richard Brooks
Starring: Glenn Ford, Anne Francis, Louis Calhern, Margaret Hayes
Genres: Drama
Deliberate mistake: Glenn Ford strikes the window in the library door with his briefcase and it instantly shatters. In reality, a blow delivered by a briefcase to a plate glass window would have produced no more than a scratch or crack.
Anne Dadier: I was like one of the bad kids in your class. Somebody told me a lie and I believed it. One's as bad as the other.