The rising demand for dual-language immersion (DLI) programs, which offer core instruction in two languages from early grades onward, has raised questions about program design and access. We leverage the rapid expansion of DLI schools across the U.S. state of Utah to estimate effects of DLI program availability on the academic achievement of primary English speakers and English learners (ELs) in programs that serve mainly the former (one-way) or at least a third of the latter (two-way). Using within-school variation in first graders' access to DLI programs, we find no overall effects on English, math, or science scores from grades 3 to 6. However, ELs whose primary languages match the schools' partner languages in two-way schools show notable outperformance in math and higher English-language proficiency at grade 5. Benefits of DLI access are driven by schools with a larger share of primary speakers of the partner language. [This paper will be published in "The B.E. Journal of Economic Analysis and Policy."]