The Impact of Class Size on Student Success: The Importance of Controlling for Instructor and Course Characteristics

Recent policy debates have focused on class size as an explanatory variable that may, or may not, influence student achievement. This research paper reviews the literature on class size, and examines the impact of class size on successful course completion when controlling for instructor and class specific variables, the gender and ethnicity of a student, the reading abilities of students, the time a course is offered, and the length of time an instructor has been teaching. Results indicate that across the sections taught by the same instructor, class size does not have a statistically significant impact on successful course completion. Students are as likely to earn a successful grade in a 20-seat section as an 80-seat section. The most important explanatory variables for student success are whether the student appeared to be “transfer directed” (a fulltime student), and whether the student had sufficient reading skills. White students performed slightly better in the courses, raising questions about the possibility of latent ethnic biases on the part of the instructor, but further research is needed. The findings suggest that for a narrow subset of classes in one social science discipline (taught by one instructor), class size has little meaning for explanations of why some students are more successful than others.