Despite nationwide advances in special education service delivery practices, disparities exist between the educational outcomes of students with disabilities versus students without disabilities. There is often disparity in teachers' roles and instructional practices in coteaching classrooms, as well as in their pullout resource classroom strategies. This descriptive case study used a mixed methods approach to explore differences in service delivery practices between coteaching and pullout resource classrooms in 3 high schools. The theoretical framework included pragmatist and constructivist approaches. A sequential exploratory design was applied to explore 3 areas: (a) instructional practices in cotaught classes, (b) instructional practices in pullout resource classes, and (c) differences in instructional practices between cotaught and resource classrooms. The qualitative sequence included thematic coding of data from 12 classroom observations and the quantitative sequence included descriptive analysis of 41 instructional practice teacher surveys. Findings indicated 3 interventions consistently implemented in cotaught classes: reteaching, strategy instruction, and hands-on curriculum materials. In pullout resource classes, there was pronounced use of reteaching and higher frequency of skills remediation than in cotaught classrooms. Special education coteachers executed less primary instruction in general settings than in resource settings. Based on these findings, a comprehensive staff development program was designed for teachers of students with disabilities to define roles, improve service delivery, and ultimately improve the educational outcomes of students with disabilities. [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.]