Acknowledgement

ii This study investigated trends in the mean ACT Assessment scores of 450 public high schools in Illinois and Iowa, according to how they scheduled classes. The schools continuously employed either a traditional eight-period daily schedule, 4x4-semester schedule, or an eight-block alternating-day block schedule. Seven years of data were available for the blocked schools, representing two years pre-implementation through four years post-implementation. The eight-period schools demonstrated a slight upward trend in mean ACT scores over time, regardless of content area. The eight-block schools demonstrated some variability in mean ACT scores, but increased little over time. After reaching a peak at or near the year of implementation, the 4x4-semester block schools demonstrated a generally declining trend in mean ACT scores across tests. With the exception of Reading, mean ACT scores rebounded somewhat at the fourth year post-implementation for the 4x4-semester block schools. ii