Many phenomena have shaped mathematics education over the past five decades, including the "new math," "back to basics," and standards movements, as well as rapidly advancing technology. Throughout his career, Zalman Usiskin witnessed, participated in, and responded to these developments, reaching teachers, mathematics educators, and the international education community. Few have had Usiskin's talent and willingness to offer opinions and guidance to inform improvement efforts in school mathematics. Currently professor emeritus, University of Chicago, Usiskin devoted a significant portion of...