This study assesses the long-term linguistic and academic outcomes associated with different bilingual language education models for low-income dual language learners (DLLs) residing in a bilingual, bicultural context. As part of the Miami School Readiness Project (MSRP), we analyzed the impact of program model on gains in English language proficiency and 5th grade standardized achievement in reading and math and grade point average (GPA) for five cohorts of DLLs followed throughout elementary school. Participants had been enrolled in public pre-K programs or received childcare subsidies to attend center- or family-childcare from 2002 to 2007 in Miami-Dade County, Florida (N = 20,870). Controlling for several student-level background variables correlated with educational outcomes, correlational and multiple regression analyses revealed that bilingual, rather than monolingual, forms of instruction were associated with acquiring English faster and superior performance in all measures of 5th grade academic achievement. Importantly, two-way immersion models that support the home language and culture and integrate language majority and minority learners were associated with faster English acquisition, which mediated the link between Two-Way Immersion (TWI) programs and higher GPAs. We discuss the implications of our findings for educational policy and practice and highlight future research directions.