This causal comparative study compared reading achievement of middle school students with disabilities (SWD) who were served in the resource class with the reading achievement of middle school SWD who were served in the co-teaching class. Reading achievement of SWD in grades six through eight was statistically analyzed to measure gains made by both groups of students. The learning outcomes were compared using reading assessment scores from the Georgia Criterion-Referenced Competency Test (CRCT) and student Lexile levels. The participants were 157 sixth through eighth grade SWD. The findings suggest that SWD may benefit equally from either instructional setting. Students from each setting made similar gains in reading achievement on the CRCT and in Lexile levels. [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.]