When Jamie Lee Curtis is teaching a class, just prior to the class trip, a shot over her shoulder shows on the blackboard 'W.B. Yates'. It should be spelled 'Yeats'. In a shot a few seconds later the spelling has been corrected.
The trivia and in jokes abound in this film. Firstly, you have Janet Leigh (Jamie Lee Curtis' mother) playing Norma (reference to Psycho) and complaining that the "showers are blocked again" (second reference to Psycho). In her last scene in the film, Janet Leigh is about to get into and drive away in the same car that she used in Psycho.