Graduation

So I was telling the boys last night that Nick wouldn't be home because he was at graduation, he teaches in a high school. Then I asked them if they knew what graduation was? Cullen piped up with, "Yes, it means you retire from school. Aunt Colleen just graduated." (Cullen just learned about retirement because one of my best friends that I teach with just retired.) I smiled and explained a little more about graduation and what can happen after, etc. After I finished talking with the boys it was silent in the car. A few minutes later Cullen announced, "I think I'm going to retire from riding my bike."