When I was in high school, every teacher had a 24-hour cooling off period after they returned tests or papers.
The idea was simple: in order to prevent whiny private school teenagers from raging against them over their bad grades, they refused to discuss any grades until 24 hours had passed. What ended up happening was that the original emotion of anger would generally pass in that time period and teachers wouldn't have to deal with any complaining. Teenagers are fickle. The teachers knew that. Ergo, they used it to their advantage.
Well, they used it for most kids.