Legislative amendments contained in the most recent reauthorization of IDEA and NCLB have mandated that all students, including those with special needs, be taught by an appropriately certified teacher. Specifically, both of these laws require that teachers of special education students in core academic classes must meet state special education certification requirements. Yet, almost no empirical research exists related to teacher certification and its relationship with special education student achievement. If certification of teachers does enhance student achievement for those with special needs, then not ensuring that those teaching special education students have certification limits academic achievement and exacerbates achievement gaps. Conversely, if no relationship exists between certification and the academic achievement of special education students, then certification requirements impose unjustified time, financial, and opportunity costs on potentially talented teachers. Drawing upon the Social Model of Disability, Vygotsky's Theory of Defectology, and the Education Production Function theory, this study investigated the relationship between teacher certification and language arts, mathematics, and science achievement for students with special needs. The study also examined whether effects differed for racial minorities or economically disadvantaged students and the extent to which teacher characteristics mediated the effects of teacher certification upon student achievement. The sample consisted of all special education high school students who took an English I, Algebra I, or Biology End-of-Course exam in the state of North Carolina during the 2004-05 academic year (n = 14,161). To estimate the relationship between teacher certification and academic achievement for students with special needs across content areas, hierarchical linear modeling of matched student-teacher data provided by the North Carolina Department of Public Instruction to the Carolina Institute for Public Policy was employed. Analysis revealed that variation in teacher certification effects exist across content areas. In English I, special education high school students taught by a teacher with special education certification or dual certification (i.e., special education certified and in-field certified) outperformed comparable students taught by teachers without special education certification or dual certification. In Algebra I and Biology, special education high school students taught by a teacher certified in-field outperformed their peers taught by a teacher not certified in-field. Moderation and mediation results also varied across the content areas. In-field certification effects were moderated by economic disadvantage, but only in Biology. No other moderation effects were detected for economically disadvantaged students or for racial minorities. More years of experience partially mediated the relationship between special education certification and English I achievement, between dual certification and English I achievement, and between in-field certification and Algebra I achievement. Advanced degree partially mediated the relationship between in-field certification and Algebra I achievement and between in-field certification and Biology achievement. None of the other variables mediated the relationship between teacher certification and special education student achievement. It is argued that detected variations are due to differences in content versus pedagogical knowledge, instructional practices, and the manner in which teachers become fully certified. Based on these results, practical implications for policymakers, researchers, and educators are discussed. [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.]