Principals are busy, and we have shown that historically they have spent little time supervising teachers. Yet policy makers are urging principals to spend more time in classrooms because they now know that teachers matter for student learning and because we have “better” tools for assessing individual teachers’ effects on student learning. Are principals prepared to do this? We noted that principal preparation programs have not devoted much time to helping principals develop observational and feedback skills. So it is not surprising that little data supports the belief that principals can improve teaching and learning. Furthermore, some argue that principals do not understand the literature on effective teaching. Such problems do not deter policy makers who at least implicitly suggest that principals’ lack of knowledge can be bypassed by giving them an observation instrument that can do the thinking for them. Unfortunately, their beliefs in the utility of classroom observation instruments are flawed. Simply put, these instruments weakly predict teacher effects on student achievement (even when used by well-trained raters), provide inconsistent results, tell us virtually nothing about teacher interactions with individual students, and provide limited information to improve instruction.