Previous research has indicated benefits and potential pitfalls of within-class homogeneous and heterogeneous ability grouping for elementary math learning. However, there has been scant evidence with regard to the impacts of grouping for language minority kindergartners who may experience the small group setting differentially due to their particular needs for math and English language skill development. Analyzing the Early Childhood Longitudinal Study-Kindergarten cohort data, we find that heterogeneous grouping or a combination of heterogeneous and homogeneous grouping under relatively adequate time allocation is optimal for enhancing teacher ratings of language minority kindergartners' math performance, while using homogeneous grouping only is detrimental. As hypothesized, suboptimal instructional organization seems to place language minority kindergartners in a vulnerable situation.