The Growth of Dual-Language Programs
Dual-language immersion (DLI) programs — in which students receive instruction in two languages throughout the school day — have grown rapidly in the US over the past two decades. The Center for Applied Linguistics estimated approximately 3,500 dual-language programs operating in US public schools as of 2024, up from around 260 in 1987. Spanish is by far the most common partner language, though Mandarin, French, Japanese, Korean, and Portuguese programs exist in various districts.
The growth reflects both research on cognitive benefits and demand from families seeking bilingual education for both Spanish-speaking students and English-speaking families who want bilingual outcomes.
Types of Bilingual Programs: Not All Are Equivalent
Two-Way Immersion (TWI)
The most rigorous model: approximately 50% of students are native English speakers and 50% are native speakers of the partner language. Both groups learn academic content in both languages. This model produces the strongest bilingual outcomes because it creates authentic peer language models for both groups. Students typically receive 90% instruction in the partner language in early grades, gradually shifting toward 50/50 by upper elementary.
One-Way Immersion
All students share the same home language (typically English), and content is taught in the partner language. More common than TWI but produces somewhat weaker bilingual outcomes because students lack native-speaker peer models in the partner language outside the classroom.
Heritage Language Programs
Designed for students who have some exposure to the partner language at home (heritage speakers) but are more dominant in English. These programs develop academic literacy in both languages for students who have cultural connection to the partner language.
Transitional Bilingual Programs
These are not true dual-language programs — they use the student's home language temporarily while building English skills, with the goal of transitioning to English-only instruction. These programs have largely been replaced by more effective models in districts with the resources to implement them.
What Research Shows: Cognitive Benefits
The research on bilingualism and cognitive development has accumulated substantially over the past 20 years:
- Executive function: Multiple studies find bilingual individuals show advantages in tasks requiring selective attention, cognitive flexibility, and inhibitory control — the "bilingual advantage" in executive function. The magnitude is debated, but the direction of the effect is relatively consistent.
- Metalinguistic awareness: Bilingual children develop stronger understanding of how language works — phonological awareness, grammar concepts, and reading comprehension skills — that transfer across languages.
- Cognitive reserve: Longitudinal research suggests lifelong bilingualism is associated with delayed onset of dementia symptoms, with some studies finding a 4–5 year delay on average.
Academic Outcomes: The Long-Game Effect
A critical finding for parents considering DLI programs: academic outcomes typically show a dip in early elementary grades, followed by strong long-term gains. Students in immersion programs often score below grade-level peers in English literacy through 2nd or 3rd grade — because they're devoting cognitive resources to two languages simultaneously. By 4th-5th grade, they typically match or exceed comparable peers in English, while also being proficient in the partner language.
This "wait for the payoff" dynamic means DLI programs are a poor choice for families seeking immediate academic gains or for students who are struggling academically and need intensive support in English.
Long-term research (through high school and beyond) consistently finds DLI graduates outperform comparable students on standardized tests, have higher graduation rates, and are more likely to attend college — though again, selection effects (motivated families) make pure causal claims difficult.
Dual-Language Programs and English Learners
For Spanish-speaking English Learner students, two-way immersion is the gold standard intervention based on research by Virginia Collier and Wayne Thomas (spanning 23 years of longitudinal data). Their research found EL students in TWI programs reached grade-level performance in both languages by 5th–6th grade and sustained that performance through high school — dramatically outperforming EL students in English-only programs or transitional bilingual programs.
How to Find Dual-Language Programs
- Check your school district's magnet or school choice page — dual-language programs are often offered as magnet programs with district-wide enrollment
- Search the Center for Applied Linguistics' Directory of Two-Way Bilingual Immersion Programs in the U.S. (freely available online)
- Contact your district's EL or multilingual education office directly
- Search MySchoolPeek for schools in your target area and review program descriptions
DLI programs often have waitlists — in many cities, demand significantly outpaces available seats. Starting the application process as early as pre-K enrollment gives your child the best chance of access.
Is DLI Right for Your Child?
DLI works best for students who:
- Are academically on track (the early-grade dip is manageable; struggling students may fall further behind)
- Have parents who can support the partner language at home (or at minimum, are enthusiastic about the commitment)
- Are entering in kindergarten or 1st grade (entering in later grades is possible but harder)
- Will stay in the program through at least 5th grade — the benefits compound with continuity