The shift from the traditional self-contained classroom to the departmentalized classroom structure in upper-elementary classrooms is increasing as the pressure to maximize student outcomes is higher than ever for public schools. Teachers prefer departmentalization but findings as to its benefits for students are mixed. This study considers the relationship between classroom structure and student achievement and whether the relationship varies by student socio-economic status. Using fourth grade data from one school district in Florida, we use Ordinary Least Squares (OLS) regression and logistic regression to examine the relationship between departmentalization and three measures of student achievement based on the Florida Standards Assessment. The findings indicate a negative relationship between all three measures of student achievement and classroom structure with some variation by student socio-economic status.