The purpose of this study was to examine if differences exist in student learning outcomes between students who are instructed in a co-taught or non co-taught environment in secondary social studies classrooms implementing Content Enhancement Routines (CER). This study examined student and teacher data from seventeen matched pairs of co-taught and non co-taught middle and high school general education social studies teachers who participated in professional development in CER and professional development in co-teaching if applicable. Of the 34 participating teachers, 23 were visited by school district personnel to verify implementation of CER. Five co-teaching teams, each consisting of a general and special educator, completed a Coteaching Rating Scale (CtRS) (n=10) to analyze the level of co-teaching occurring in the classroom (beginning, compromising or collaborating stage). A systematic sample of students (n = 907) completed a CER Student Perception Survey to examine perceived differences of the use of CER in co-taught and non co-taught social studies classrooms. Student state assessment scores (n = 318) in co-taught and non co-taught classrooms were analyzed to distinguish differences in student learning gains. Specifically this study investigated if differences in student performance occur when a special educator is present in the classroom. Results indicate that although there was no statistically significant difference in student learning outcomes between the two settings, the impact of teacher preparation, professional development and the implementation of CER in the secondary social studies classroom may be determining factors in student success.