Sixteen states have adopted school report card accountability systems that assign A-F letter grades to schools. Other states are now engaged in deliberation about whether they, too, should adopt such systems. This brief examines A-F accountability systems with respect to three kinds of validity. First, it examines whether or not they are valid as a measure. That is, do these systems validly measure school quality? Second, it examines whether or not they are valid as a policy instrument.