Externalizing behaviors are associated with poor academic outcomes in community-based samples of children as young as preschool-age. However, there remains debate as to which specific externalizing dimensions link externalizing behaviors to early academic skills. Recently, research has supported the use of S-1 bifactor models to examine the hierarchical structure of externalizing behaviors and the unique relations between externalizing factors and academic impairment in samples of school-age children. The primary goals of this study were to extend the age range at which S-1 bifactor models are applied to externalizing behaviors and to determine if factors derived from an S-1 bifactor model had differing relations to early academic skills. In this study, the early academic skills of 1,356 preschool-age children (mean age = 49.98 months; SD = 8.08) were assessed, and preschool and childcare teachers rated children’s externalizing behaviors. Results indicated that an S-1 bifactor model with a Hyperactive Impulsive reference factor yielded the best-fitting model for preschool-age children’s externalizing behaviors. Structural models revealed that both the Hyperactive-Impulsive reference factor and the Inattention factor uniquely predicted preschool children’s early academic skills. The degree to which the results applied across the primary groups in the sample (i.e., White versus Black/African American children, girls versus boys) was examined for measurement and structural models. (author abstract)