I actually knew a guy who did this in High school. Well, he mooned the entire 12th grade AND the parents AND the schoolteachers and admins all at once. He was able to do that because this was our graduation.
Our assistant principal, a total jerk at the best of times, jumped up and yelled, “YOU’RE EXPELLED, YOU LITTLE A*#HOLE!”
And the student calmly responded, “I just graduated. *You can’t touch me, s#*head!” And the students (and parents) howled with laughter.
Last I saw him the cops were dragging him away… and even they were laughing.