The theories in Psychology, Dream an Sleep branch is not confirmed, so you can say whether you believe in this theory or that theory, as long as you can say what points of view to support you to believe that theory.
Because of that reasons, students can do an inter-class debate between various theories about the functions of dream and sleep. Before that, students can do research for that specific theory.
Examples of debate topics are:
1. Functions of Sleep
Neuro-physiological model / Learning and Remembering model / Forgetting model
2. Functions of Dreams
Theories of Freud / Jung / Perl / Boss / Gestalt
Another way of learning these theories:
After discussing various sleep or dream theories, post them on the walls of the room, distribute index cards listing interesting experimental results, and ask students to post each card under the theory that the research best supports.