The enactment of No Child Left Behind (2002) and the reauthorization of the Individuals with Disabilities Education Act had a significant impact upon how we hold schools and its students accountable for high stakes testing. In particular, students with educational disabilities who were previously exempted from any performance accountability on high-stakes testing are now required to pass the same standards-based assessments as their general education peers. This action research study was prompted by concerns of school leaders who identified an immediate need for instructional reform for students with educational disabilities was necessary. The study design was to examine the impact of the inclusion co-teaching model of instruction on high-stakes testing for students with educational disabilities. Guiding the study were the perceptions of co-teachers within the inclusion classroom and how this also impacts assessments. It also explored the self-esteem of these students who are in an inclusion co-teaching program. The collection instrumentation that supported this action research study consisted of teacher and student surveys, student interviews, teacher interviews, teacher focus groups, case manager interviews, end-of-year final grades, New Jersey Department of Education School Report Card and archival assessment data. This course of action provided both quantitative and qualitative data. The research yields credence for placing students with educational disabilities into inclusion co-teaching environments to increase academic proficiency on high-stakes assessments. Research findings revealed that a significant increase in the self-esteem of students with educational disabilities in inclusion classrooms and the perceptions of co-teachers all contributed to an increase in academic proficiency. [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.]