The effects of modified school calendars on student achievement and on school and community attitudes

This review synthesizes studies of the effects of modifying the academic calendar in Grades K-12 to do away with the long summer break while not increasing the length of the school year. The synthesis indicated that the quality of evidence on modified calendars is poor. Within this weak inferential framework, the average effect size for 39 school districts was quite small, d = .06, favoring modified calendars. Studies that used statistical or matching controls revealed an effect size of d = H. Modified calendars were associated with higher achievement for economically disadvantaged students. Students, parents, and staffs who participated in modified calendar programs were positive about their experiences. Policymakers can improve acceptance of modified calendars by involving communities in the planning and by providing quality intersession activities.