Brookhart maintains that clear, positive teacher feedback, which provides precise information on the next steps a student can take to reach their learning targets, is at the heart of formative assessment. Because feedback is closely tied to students' feelings of self-efficacy, it can be destructive as well as motivating. Drawing on research and her own experiences as an educational consultant working on assessment issues, Brookhart describes what she thinks makes for powerful feedback--both in terms of how it's delivered and its underlying message. Good feedback focuses on both the work and the student's process; relates feedback to a learning goal; describes work products rather than passes judgment; and is positive and specific. Brookhart gives an example of both unhelpful and helpful feedback on one elementary student writing sample. (Contains 2 figures.)