Morgantown (West Virginia) High School developed and implemented a collaborative teaching service delivery model, in which special education students enrolled in given subjects were mainstreamed into regular classes. A regular educator and a special educator were jointly assigned to the classroom to team teach the curriculum. The special and regular educators were jointly responsible for choosing teaching methods, curriculum formats, learning strategies, study skills, and evaluation methods for all students. The regular educator contributed expertise in content matters, whereas the special educator contributed expertise in learning, modification, and evaluation strategies. This paper evaluates whether the program was an effective teaching tool. Fifteen classes were included in the evaluation, involving eight regular educators, five special educators, and a total of 318 students. Special education students had learning disabilities, hearing impairments, behavior disorders, mild mental impairments, or limited English proficiency. Results are analyzed in terms of reading comprehension scores, previous grades in traditional classes, grades in the collaborative teaching program, comparison by student category, teaching team and content area interactions, mean grade point overall and by content area, and grade changes for individual students. Analysis indicated that all students in the Collaborative Teaching Program performed equivalently, despite substantially poorer reading comprehension scores of special education students. All students' grades improved after their enrollment in collaboratively taught classes. (JDD)