A research study was conducted to compare the academic achievement of third grade students in an extended year school to that of third grade students in a conventional school. Variables such as summer breaks, socioeconomic status, and student attendance were also examined. Results of the study indicated that there was an association between the type of school calendar, extended versus conventional, and the academic achievement of elementary students as measured by student scores on the Missouri Assessment Program. Это и многое другое вы найдете в книге Extended and Conventional Year School: Effects on Academic Achievement (Vanessa Khankeo van der Graaf)