The academic achievement of high school students in the United States has remained behind in science and mathematics compared to other industrialized nations. Block scheduling is a reform movement that may increase proficiency rates of high school students in the areas of science and mathematics and increase overall high school graduation rates. This study presents the effects of 4X4 block scheduling on student achievement and continuous enrollment rates. The researcher used archival test data to determine whether a significant difference existed in the California State Standards Test (CST) scores in life science between sophomore students who attended high school on a 4X4 block schedule and those who attended high school on a traditional schedule. The results of an independent t-test suggests that sophomore students who attended high school on a traditional schedule performed significantly higher than sophomore students who attended a high school on a 4X4 block schedule. This researcher also used archival data to determine whether a significant difference existed in continuous enrollment rates between students who attended a high school on a 4X4 block schedule and those who attended a high school on a traditional schedule. The results of the Pearson chi-square suggests that students who began high school on a 4X4 block schedule were more likely to stay until they graduated than students who began high school on a traditional schedule.