Pre-assessment has a bad reputation, write Hockett and Doubet--but that's largely because it's often misused solely to compare pre- and post-results. Used this way, pre-assessment serves as little more than a thief of instruction and a discouraging exercise for students. The authors describe how teachers can design thoughtful pre-assessments that help them plan differentiated instruction and increase student mastery. Such pre-assessments (1) include just a few key questions that gauge students' understandings as well as their knowledge and skills aligned with key unit goals; (2) pique students' interest in what they're about to study; and (3) uncover potential connections between the students and the content. The teacher should plan in advance how he or she will adjust and differentiate instruction on the basis of students' answers. The article includes two pre-assessment exemplars--one for a unit on graphing and another for a unit on World War II.