Elementary instruction of fifth grade classrooms was found to be primarily in two organizational models in a school district northwest of Atlanta, Georgia. The self-contained classroom provided a generalist teacher responsible for the instruction of all academic subjects to one group of students throughout the day, while departmentalized classrooms were structured utilizing one teacher for the instruction of one or two content areas, and students rotated throughout the day for each of the academic subjects. The majority of studies looking at the effect of instructional organization were concentrated in the content areas of mathematics and reading. This quantitative study, utilized an "ex post facto" methodology to determine whether fifth grade students attending departmentalized schools or self-contained classrooms had higher student achievement in science as measured by the Georgia Criterion Referenced Competency Test (CRCT). The statistical data was collected through the Georgia Department of Education and included raw mean scores of over 500 students attending departmentalized schools and 500 students attending self-contained classrooms, along with the various subgroups such as gender, ethnicity status, English language learners (ELL), and students with disability (SWD) placement. This data was analyzed to show if a significant statistical difference emerged from either instructional organization. The overall results that emerged from the archival data suggested no significant difference in student achievement existed for almost all subgroups tested of the total 1000+ participant scores used in the study. The results also did however, showed the departmentalization model of instruction had a slight advantage over self-contained classrooms for male students with disabilities. [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.]