Elementary classrooms were found to be structured in two configurations: self-contained classroom, with one teacher teaching all academic subjects and departmentalized classrooms with two teachers teaching a portion of the academic subjects to two classrooms. These structures were found to coexist in a large urban district with whole schools operating under the self-contained or departmentalized structure. A review of the literature found that proponents of each of these structures have existed in American schools for more than seventy years and support for each has been sustained. Utilizing ex post facto research methodology, this quantitative study gathered test data in math and science to identify patterns in achievement based on these structures. Data were analyzed utilizing factors of gender, ethnicity, ESL, bilingual, and GT program participation. Statistically significant findings were found in support of departmentalized classrooms in mathematics for grade four students and third grade bilingual students. Fourth grade female ESL and bilingual students performed significantly better in self-contained classrooms for mathematics.