The question of where best to educate students with disabilities to maximize their academic achievement has been discussed and researched for over four decades, with inconsistent and contradictory results. This study focused on the mathematics and reading achievement of middle and high school students with mild disabilities in an urban district in a plains state, as measured by state assessments. The study was comprised of 430 students in the area of mathematics and 449 in the area of reading. The intent of the study was to determine if placement in inclusive settings made scoring proficient in reading and mathematics more likely than placement in non-inclusive settings. The dependent variable was the individual student's academic performance, proficient or not proficient, on state reading and mathematics assessments. The independent variable was the instructional delivery model in which each student was placed respectively for reading and mathematics instruction (general education with no support, general education with support of a special education co-teacher or paraprofessional, separate special education classroom, and separate special education school). Control variables included the student's disability category, race, gender, poverty status, and the school attended by each student. The study employed a Two-Stage Least Squares regression to estimate the odds of students scoring proficient in reading or mathematics based on their instructional delivery model. The first of two main findings was that the instructional delivery model in which a student receives instruction significantly affects performance in mathematics. For each increase in delivery model restrictiveness the odds of scoring proficient in mathematics decreased. The second finding was that the effect of instructional delivery model on reading proficiency was not significant. [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.]