Abstract: This quantitative study examined standardized test scores of second and third grade elementary students in and out of a one-way Spanish language immersion program located at a school in an affluent neighborhood in the southwestern United States. Data of reading, writing/language, and math scores on a state report card were compared to surrounding schools with similar demographics in the same district. Quantitative statistical T-tests comparing students in and out of the Spanish language immersion program at the same school were also performed in reading, writing/language, and math, to determine if students in the program were performing, equal to, or better than students in the regular English-only classrooms. Results supported the view that students in dual language immersion programs perform equal to or better in reading, writing, and math, than students in classrooms where subjects were taught only through the English language. Furthermore, results of statistical analysis suggest that students in the language immersion program had significantly higher math scores than students out of the program at the same school, on state adopted standardized tests.