Jean Piaget's moral development theory demonstrates that younger children see rules from adults as solid and can not be changed. Older children see rules as things that can be based on a mutual agreement. He discovered this by watching children play with marbles and asking them questions about it.
When I think of my childhood with their theory, I remember in school and at home rules always being very tough. Then when high school came, rules were a little different. My parents were more willing to come to agreements with me too.
This theory will be helpful as a teacher because my elementary schoolers will (hopefully) follow the rules thinking they are solid. If they do, they will be rewarded. This should help them to want to follow the rules more frequently.