All groups make up some kind of social contract. People do this because they need some kind of basic order in their lives. Social contracts are often assumed by the members of a group and little time is spent in discussing them. We often agree to social contracts without thinking about them very much. People become very uncomfortable when some important part of the social contract is violated.
People feel more comfortable when they believe they know what they can expect in a social situation.
Social contracts are always enforced in some way. Groups are prepared to be very ruthless in enforcing conformity when their sense of what is right and wrong is offended. Have the students develop a hypothesis which defines their conception of good manners and then use their analysis of social organizations above to test whether their hypothesis is valid.