The number of public high schools implementing a semester 4 x 4 block scheduling design within the state of South Carolina has tripled since 2005. However, minimal local research has been conducted regarding the impact of block scheduling on student academic achievement. The purpose of this study was to determine if significant differences exist among schools in South Carolina that employ a 4 x 4 semester block schedule, an alternate A/B block schedule, or a single-period traditional schedule on school passage rates in English-language arts (ELA) and math as measured by the exit exam of the South Carolina High School Assessment Program (HSAP). Particularly, this research sought to determine whether an increase in the overall passage rate within schools utilizing a 4 x 4 semester block schedule has manifested since the inception of the High School Assessment Program (HSAP) exit exam in 2004 and local research studies since 2005. The 131 public high schools identified for participation consistently used one of the three scheduling types for the academic school years of 2005-06 through 2007-08. A mixed ANOVA yielded no significant differences in the mean ELA and math passage rates among the three types of schedules. Based on the findings of this study, recommendations for action include an emphasis on continued professional development and support for instructors teaching for an extended amount of time in the 4 x 4 semester block schedule format. Implications for positive social change are that the results of this study will encourage districts to scrutinize the research and data on block scheduling, evaluate the reason for changing to or abandoning block scheduling, and assist teachers with proper implementation of instructional strategies used in the block scheduling design in order to improve student academic achievement. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]