This longitudinal study examined the effect of all-day kindergarten programs on the academic achievement of students from racial language minority and low socioeconomic class. The study employed a series of 3-level longitudinal multilevel analyses using a nationally representative database, the Early Childhood Longitudinal Study (ECLS). The study showed that Hispanic dual-language-speaking students who attended all-day kindergarten narrowed the achievement gap from Hispanic English-only students during kindergarten. The results also showed that Black and Asian dual-language-speaking students, when they attended all-day kindergarten, displayed a significant gain in the growth of performances. The positive effects of all-day kindergarten were pronounced for Black and Asian language-minority students who were from low social classes. These results have implications for policy decisions and support the need for all-day programs for language-minority students. (Contains 5 tables and 4 figures.)