The primary purpose of this study was to determine if there was a difference between self-contained and departmentalized classroom organization on the Kentucky Core Content Test (KCCT) in reading and mathematics for students in fourth and fifth grade. A secondary purpose of this study was to consider how these organizational structures affect the KCCT scores in regard to gender, ethnicity, and socio-economic status of the students from which scores were obtained. The results of this study will provide necessary information to educational decision-makers. The review of literature, as presented in Chapter Two, indicates that few current empirical studies have been done in the area of school organization. This study will help fill the gap of research in the area of the impact on student achievement in self-contained and departmentalized school organization. The population for this project included fourth and fifth grade students from eight public elementary schools in one urban school district within the state of Kentucky. Within this district there were 88 elementary schools. The schools included in this study were selected by the researcher, because four offered a self-contained school organization and the other four offered a departmentalized school design. The data was analyzed using the Statistical Package for the Social Sciences (SPSS), and through Hierarchical Linear Modeling (HLM). Analysis of the descriptive statistics showed the two groups (self-contained and departmentalized) of schools to be similar. Random effects ANOVA, intra-class correlation, and multiple regression were used to examine both student and classroom level data. The findings from the study showed that there was no effect of group (self-contained versus departmentalized) on the academic performance of the students in either reading or mathematics KCCT scale scores. The conclusions drawn by the researcher, based on the study results were that based on the population of the study, the choice of school organization (self-contained or departmentalized) had no significant effect on the academic achievement of fourth and fifth grade students on KCCT reading and mathematics scale scores. [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.]