The author examined the long-term effects of teacher instructional grouping practices on the early mathematical achievement of language minority students from various ethnic groups. The study used 3 longitudinal models. In the 1st model, English language learners (ELLs) displayed lower math performance than did English-only students in the Hispanic and Asian groups. The 2nd model confirmed the significance of social class across all groups. The 3rd model focused on 4 grouping practices: (a) teacher-directed whole-class activity, (b) teacher-directed small-group activity, (c) teacher-directed individual activity, and (d) student-selected activity. Significant findings include that (a) Hispanic ELL students displayed low math performance in teacher-directed whole-class activities, (b) Asian ELL students showed low math performance in teacher-directed small-group activities, and (c) Hispanic dual-language students benefited from teacher-directed individual activities. (Contains 4 figures and 6 tables.)