Recent federal initiatives emphasize measuring teacher effectiveness and ensuring that disadvantaged students have equal access to effective teachers. This study substantially broadens the existing evidence on access to effective teaching by examining access in 29 geographically dispersed school districts over the 2008-2009 to 2010-2011 school years. The report describes disadvantaged students' access to effective teaching in grades 4 through 8 in English/language arts (ELA) and math, using value-added analysis to measure effective teaching. On average, disadvantaged students had less access to effective teaching in these districts. Providing equal access to effective teaching for FRL and non-FRL students would reduce the student achievement gap from 28 percentile points to 26 percentile points in ELA and from 26 percentile points to 24 percentile points in math in a given year. The main findings are: (1) On average, disadvantaged students had less access to effective teaching in the 29 study districts in grades 4 through 8. The magnitude of differences in effective teaching for disadvantaged and nondisadvantaged students in a given year was equivalent to a shift of two percentile points in the student achievement gap. (2) Access to effective teaching for disadvantaged students did not change over time in the study districts. (3) Disadvantaged students' access to effective teaching varied across school districts. (4) Unequal access to effective teaching was most related to the school assignment of teachers and students rather than to the way that teachers were assigned to students within schools. Appended are: (1) Analytic Methods; (2) Diagnostics of Value-Added Models; and (3) Additional Tables and Sensitivity Analyses for Chapter IV. (Contains 24 tables, 35 figures, and 48 footnotes.)