States are the primary policymakers in several important areas of K-12 education. Given their dominant role in educational funding and regulation, states not surprisingly have been the primary initiators of the latest wave of educational reform starting in the mid-1980s. In this paper, the authors sought to test indirectly for the effects of statewide reform efforts on student achievement by analyzing the state National Assessment of Educational Progress (NAEP) tests in mathematics at the fourth- and eighth-grade levels from 1990 to 1996. This study extends a previous analysis in two ways. The previous study utilized the state NAEP data to estimate trends across states, differences in scores across states for students from similar families, and the effect of differing levels and allocations of resources across states. This study extends the previous analysis by (1) estimating the trends by state that are unaccounted for by resources and (2) providing estimates of trends for central-city, rural, and suburban areas within states to provide additional evidence about the effects of statewide reforms. The authors produce estimates of rates of growth in mathematics achievement during 1990-1996 for individual states and the nation as a whole, controlling statistically for differences across states and over time in the demographic mix of students. They present estimates of national gains, state gains, and locality gains within states. They find that, after controlling for differences over time in the demographic mix of students, national average test scores in the fourth and eighth grades increased during 1990-1996. Comments by Philip Uri Treisman, Edward J. Fuller, and Robert H. Meyer are included. (Contains 3 figures, 14 tables, and 62 notes.)