Classroom observation is a crucial aspect of any system of teacher evaluation. No matter how skilled a teacher is in other aspects of teaching--such as careful planning, working well with colleagues, and communicating with parents--if classroom practice is deficient, that individual cannot be considered a good teacher. Classroom observations can foster teacher learning--if observation systems include crucial components and observers know what to look for. Virtually every state requires observations of teaching as a significant contributor to high-stakes judgments about teacher quality. To be defensible, the systems that yield these observations must have clear standards of practice, instruments and procedures through which teachers can demonstrate their skill, and trained and certified observers who can make accurate and consistent judgments based on evidence. In addition, it's possible to design approaches to classroom observation that yield important learning for teachers by incorporating practices associated with professional learning--namely, self-assessment, reflection on practice, and professional conversation. When these practices are put into place, classroom observation can make a dramatic contribution to the culture of a school. (Contains 2 endnotes.)