Traditional assessments--which detect and highlight differences in student learning and rank students according to their achievement--inevitably produce winners and losers. Because today's schools cannot afford to leave any child behind, educators need to embrace a new vision of assessment--one that enables all students to become winners. The author describes how assessment for learning turns day-to-day assessment into a teaching and learning process that enhances (instead of merely monitoring) student learning. Teachers share achievement targets with students and work with them in partnership to use the results of frequent assessments to move toward those targets. Rather than a one-time event stuck on at the end of an instructional unit, assessment becomes a series of interlaced experiences that keep students posted on their progress, even in the face of occasional setbacks.