This study investigated the effects of class size on the academic achievement of South Carolina's first grade students. Two classes within each of 25 school district units participated in the project. Within each of the school district units, 50 first grade students were randomly selected and assigned to the small class treatment group (class size=21 students) or the large class treatment group (class size=29 students). Two teachers within each school district unit were then randomly selected and assigned to one of the two treatment groups. Pre-testing in reading, mathematics, and language and post-testing in reading, mathematics, language, and overall achievement were done with the Comprehensive Tests of Basic Skills. In order to investigate possible confounding variables, data were also collected on student sex, race, Title I classification and kindergarten experience. Findings showed that class size did not have a significant effect on the reading, mathematics, language, or overall achievement of the first grade students involved in the project. A summary of the South Carolina First Grade Pilot Project 1975-76 is also included. (JMB)