Educational Review, vol.71, no.4, pp.501-517, 2019 (SSCI)
Determining the number of hours and days students should spend in school per year to improve student achievement has been a central policy issue, influencing, for example, authorities’ attitudes toward disciplining pupil non-attendance and fining parents for the withdrawal of students for vacations. This paper is a review of research studies on the effect of amount of instructional time. It focuses on how the amount of time spent on core subjects (mathematics, science and reading/language arts) and number of instructional days in a school year relate to students’ academic achievement. Reviewed studies give difficult-to-interpret findings. While there is a broad association between allocated instructional time and achievement, as would be expected, there is evidence that there may be a ceiling effect of instructional time and that peer composition of classrooms may mediate the effect of additional instructional time.