Although the trajectories of children's social skills have been examined across biological sexes, less research has examined these patterns for racially and ethnically diverse children in the United States. The purpose of this study was to estimate the longitudinal growth trajectories of social skills, while examining the influence of biological sex, race, and ethnic identities using an adaptation of the commonly used Social Skills Rating Scale. A large nationally representative sample of elementary school children in the United States were assessed annually from kindergarten through fifth grade (N = 11,792). Structural equation modeling was used to examine latent growth curve models of teacher-rated interpersonal skills and self-control. After finding evidence of longitudinal invariance, results suggested a quadratic growth pattern best represented the trajectories of social skills ratings. Teacher ratings for African American children demonstrated a moderate declining linear trajectory throughout elementary school when compared with White children (reference group) and their Asian and Hispanic peers. Children from families with higher socioeconomic status and girls showed moderate to large differences in social skills ratings in kindergarten and stronger growth across time. Implications of the findings with future directions for research are discussed.