Contemporary research on teaching indicates that teachers are powerful contributors to students' academic achievement, though the set and interrelationships of characteristics that make for high-quality and effective teaching have yet to be satisfactorily determined. Nevertheless, on the basis of the extant research and a vision of exemplary teaching, the National Board for Professional Teaching Standards stipulated a definition of a superior teacher. The Board did this without empirical evidence to support their claim that teachers' who meet the standards set by the Board were superior in promoting academic achievement to those who did not meet those standards. In the 17 years since the founding of the National Board, only a few empirical studies have addressed this important issue. In this study we compare the academic performance of students in the elementary classrooms of 35 National Board Certified teachers and their non-certified peers, in 14 Arizona school districts. Board Certified teachers and their principals provide additional information about these teachers and their schools. Four years of results from the Stanford Achievement Tests in reading, mathematics and language arts, in grades three Board Certified Teachers and Student Achievement 2 through six, were analyzed. In the 48 comparisons (four grades, four years of data, three measures of academic performance), using gain scores adjusted for students' entering ability, the students in the classes of National Board Certified Teachers surpassed students in the classrooms of non-Board certified teachers in almost threequarters of the comparisons. Almost one-third of these differences were statistically significant. In the cases where the students of non-Board certified teachers gained more in an academic year, none of the differences found were statistically significant. Effect size, translated into grade equivalents, informs us that the gains made by students of Board Certified teachers were over one month greater than the gains made by the students of non-Board certified peer teachers. Teachers identified through the assessments of the National Board for Professional Teaching Standards are, on average, more effective teachers in terms of academic achievement, one of the many outcomes of education for which teachers are responsible. This study does