Prior research suggests that exposure to elementary classrooms characterized by high levels of student aggression may contribute to the development of child aggressive behavior problems. To explore this process in more detail, this study followed a longitudinal sample of 4,907 children and examined demographic factors associated with exposure to high-aggression classrooms, including school context factors (school size, student poverty levels, and rural vs. urban location) and child ethnicity (African American, European American). The developmental impact of different temporal patterns of exposure (e.g., primacy, recency, chronicity) to high-aggression classrooms was evaluated on child aggression. Analyses revealed that African American children attending large, urban schools that served socioeconomically disadvantaged students were more likely than other students to be exposed to high-aggressive classroom contexts. Hierarchical regressions demonstrated cumulative effects for temporal exposure, whereby children with multiple years of exposure showed higher levels of aggressive behavior after 3 years than children with primacy, less recent, and less chronic exposure, controlling for initial levels of aggression. Implications are discussed for developmental research and preventive interventions.