If a teacher is teaching a unit on mysteries, can she/he show short movie "clips" from several mysteries to the class?
The teacher can show clips from mysteries to his/her class if the tapes are set to show the clip on every separate tape that he/she is showing the class. For example, press "play", watch the clip, pop out the tape and put the next tape in.
The teacher would NOT be able to make a new tape with just clips of famous mystery movies. That would be considered making an anthology and is against copyright laws.