Mistake: A student raises her hand to announce that there’s a typo on a handout.

Knee-Jerk Reaction: Saying “I did that on purpose just to see if you guys were paying attention.”

Constructive Response: Reward the student who discovered the typo. Ask the whole class to correct the error on the handout by hand. Then have them look for more typos, turning the moment into an editing exercise. —Mike Arnzen —Competence is What You Do When You Make a Mistake (Pedablogue)