The purpose of this study was to determine the effect of explicitly differentiated reading instruction groups on eighth-grade students' achievement, behavior, and engagement in a school seeking to reestablish adequate yearly progress benchmarks. The results of this study supported student participation in explicitly differentiated reading instruction groups. Because students in High Reading Ability (n = 25), Middle Reading Ability (n = 25), and Low Reading Ability (n = 25) groups maintained average to above average achievement test scores on several measures with commensurate classroom grade performance, and appropriate behavior and engagement to support school success during eighth grade, the results suggest continued implementation of explicitly differentiated reading instruction classrooms. Faced with the imperative to acquire literacy skills adequate to meet the academic demands of the high school educational process and post-secondary life as either college student or working adult, learning must be accelerated for all segments of the student population. Additionally, this acceleration is fundamental to the school's ability to meet No Child Left Behind requirements and attain levels of student achievement commensurate with legislative expectations. Researchers have clearly developed answers for pedagogical questions surrounding which instructional components enable and accelerate the development of critical reading skills that include differentiated instruction that is intensive and frequent. Moreover, practitioners are cautioned that traditional classroom instruction may not provide enough of these components to accelerate learning and skills acquisition. The results of this study suggest that when these critical components are present in the daily educational routine, supported by the student schedule and teacher roster assignment, achievement can be significantly positively influenced. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]