This article discusses findings of a study conducted in an urban Title 1 elementary school in the United States. The study examined mathematics quarterly test data from Hispanic newcomer English language learners (ELLs) enrolled in Grades 4 and 5 at the same school, some of whom received mathematics instruction almost entirely in Spanish (treatment group) and some in English (comparison group). The treatment group (n = 15) and the comparison group (n = 48) were not randomly selected. A selection criterion was used instead. As predicted, and consistent with research on language transfer theories (Cummins, 1981), empirical data revealed that Hispanic ELLs receiving mathematics instruction in Spanish exhibited higher gains (7%) when compared to those receiving that instruction in English (<3%). As the ELL population continues to grow (Chishti & Hipsman, 2016), these findings may offer an alternative to those interested in closing academic opportunity/achievement gaps.