This book examines the intersection of policy and practice in the use of student growth measures (SGMs) for high-stakes purposes as per such educator evaluation systems.  The book also focuses on examinations of educators’ perceptions of and reactions to the use of SGMs; ethical implications pertaining to the use of SGMs; contextual challenges when implementing SGMs; and legal implications of SGM use. The use of student test score data has been the cornerstone of the recent transfiguration of educator evaluation systems in forty-two states and the District of Columbia. Three leading voices on SGMs—Sean Corcoran, Henry Braun, and David Berliner—also serve as section and concluding commentators.