(1) A teacher argues for allowing students to redo certain quizzes for partial credit. (2) Redoing helps students learn from mistakes instead of moving on with gaps. (3) After redos were allowed in one unit, the number of students scoring below 70% on the final dropped from 12 to 5. (4) Some students claim redos are unfair to those who studied the first time. (5) The teacher responds that the goal is mastery, and redos still require extra work.