I agree with Kaylee. My little brother gets away with everything he does because he says he'll never do it again. Guess what? He does something worse. People who know they won't get punished deserve whats coming to them.
If a student does not complete an assignment, they should deserve time to finish it after school. It's not a punishment, its just that students wasted a teachers time to not do i,t so they should sacrifice their time to finish.