Despite the billions of dollars spent in the last forty years, America's efforts toward closing the achievement gaps among diverse learners and their receptive counterparts have not been realized. Limitations noted in previous research discussed the need to examine the unique contributions of diverse learner variables as a way of determining their specific academic needs. The purpose of this study was to examine the intra- and inter-group growth trajectories of two diverse student groups (English Language Learners and Students with Specific Learning Disabilities) on reading achievement. The study employed a longitudinal, quasi-experimental research design utilizing archival data from 26,947 students' files to answer two research questions. The first research question examined growth relationships between 3rd grade English Language Learner student categories on reading achievement while holding gender and socio-economic variables constant. The second research question explored the extent to which the initial levels and slopes of 3rd grade students with specific learning disabilities differed across racial and ethnic groups. Growth curve analyses were employed to answer both research questions. Findings revealed significant intercept and slope relationships for the two groups on reading fluency measures. Significant differences were found between the reference group (i.e., Non-ELL females who were ineligible for free and or reduced lunch) and two of the ELL subgroups. The slope relationships were only significant for ELL students (ELL-LY) who were in the currently enrolled (i.e., receiving some type of ELL instructional support or service) category. Gender and socio-economic variables were significant suggesting a negative influence on initial reading levels. Reading fluency (DORF) achievement findings relative to students with disabilities and their race and ethnic subgroups revealed White students' initial DORF scores were significantly different from Hispanic and Black students' scores. Race and ethnic slope variables were insignificant and homogeneous in nature. A discussion about these findings and their implications for closing the achievement gap for diverse students is provided in the document. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]