Continuity mistake: When the kids first react to Delores scraping her nails on the blackboard, a girl near the front of the class, (later revealed as 'Maria') wearing sunglasses, is in the process of sitting in a chair. When Delores then asks them to put the desks back, she is now sitting on top of a different desk further to the right, is now holding a magazine and no longer wearing sunglasses. The short time elapsed makes it impossible for her to have moved.
Audio problem: At the contest in Hollywood, when the priest pushes Mr. Crisp into the closet he says, "Forgive me," but his lips don't move.
Sister Mary Clarence: Hey Father Thomas, what's happenin'?
Father Thomas: What's happening is I've been sent to deliver a message like I'm working for Western Union instead of the Roman Catholic Church.