In 2023, it’s clearer than perhaps ever before that facts have lost much of their power in shaping political debates. In recent years, American democratic discourse has become so unmoored from testable, verifiable facts that researchers have begun warning that the U.S. body politic is suffering from “truth decay.”

This is a trend worth resisting. A self-governing country that relies on elected officials to represent their views and make decisions on matters of public importance must have a stock of common facts. How else can voters accurately identify collective challenges and elect leaders with serious solutions?

If there’s any place where facts should definitely guide decisions, though, it is in education policy. Nonetheless, facts seem to have a hard time getting a public hearing there as well. In Arizona, state education leaders are currently embroiled in a debate—recently elevated to a lawsuit—over how schools can best serve English learners (ELs). Arizona’s history has been multilingual for many centuries—one-quarter of the state’s children speak a non-English language at home. So the public unquestionably has a stake in ensuring that schools offer programs to help ELs succeed.

Fortunately, unlike many political debates, the question at the heart of this struggle, “What’s the best way for schools to help the most ELs acquire English and succeed academically?” is essentially an empirical one, which research has largely answered.

Before reviewing the answer to that question and what it means for Arizona, however, it’s helpful to survey the state’s political and historical context on EL education.

Arizona’s Twenty-Year Experiment

In a 2000 referendum, Arizona voters passed Proposition 203, which mandated “structured English immersion” programs for English-learning children in all of the state’s public schools. The state’s implementation of this proposition produced a daily four-hour English immersion block, during which ELs were segregated away from their non-EL peers—and away from the academic instruction going on back in their mainstream classrooms—to study English directly. Since this model’s supporters believed that this English-only immersion would bring ELs to English proficiency quickly, it was designed to withdraw language instruction support after one year.

Arizona’s English-only model has come under heavy and sustained criticism on many grounds. First, it overtly and intentionally segregates ELs from their non-EL peers. Second, it isolates ELs’ linguistic development from their academic development, teaching students English in a vacuum, separate from other academic content instruction and their school’s broader social community. Indeed, the U.S. Department of Justice and the U.S. Department of Education’s Office of Civil Rights eventually intervened (several times) to force Arizona to alter the English immersion program to comply with civil rights law.

In 2019, in response to these critiques, a bipartisan group of Arizona legislators crafted SB 1014, a measure to give local school districts more flexibility in designing language instruction models for their ELs, and then-governor Doug Ducey (R) signed it into law. This has led to the launching of an array of new language instruction models, including some bilingual programs such as dual-language immersion schools.

Arizona’s current debate—particularly the recent lawsuit—is at its core a political fight over who, precisely, gets to determine the range of language instruction models in Arizona. Is it the current state superintendent of public instruction, Tom Horne? Or is it the Arizona State Legislature?

Perhaps the recently filed lawsuit will settle that fight. But regardless, all involved should acknowledge that the answer to the empirical question behind the fight—“What’s the best way for schools to help the most ELs acquire English and succeed academically?”—is pretty much settled science.

Facts: The Research Consensus on ELs’ Linguistic and Academic Development

Since 2000, there have been a raft of studies—of increasing methodological rigor—on how ELs best learn English and academic content in U.S. schools. The research community’s most robust answer to this question came in 2017, when a comprehensive, rigorous consensus study from the National Academies of Sciences, Engineering, and Medicine concluded that English-only programs are not the better choice: “[S]tudies that compare outcomes for [ELs] instructed in English-only programs with outcomes for ELs instructed bilingually find either that there is no difference in outcomes measured in English or that ELs in bilingual programs outperform ELs instructed only in English.”

For those who are not regularly engaged with research on language acquisition, this can seem counterintuitive. After all, if the goal is for EL students to learn English, presumably schools should surround them with as much English as possible—that is, with monolingual English-only instruction. This is more or less the position presently advanced by Superintendent Horne.

But intuitive theories turn out to be wrong all the time. The sun sure seems to rise in the morning, travel across the sky, and set in the evening, but in fact, Earth is the body doing the relevant orbiting (and the rotating). That’s why researchers gather data—to figure out whether or not decision makers should trust their intuition.

And when it comes to studies of different instructional models, researchers generally find a stable pattern in their data: ELs are more likely to reach English proficiency and be reclassified as former English learners when they have access to multilingual instruction. For instance, a 2014 study in a California district found that ELs in dual-language programs were more likely to reach English proficiency than their peers in English-only settings by middle school—and the gap favoring dual-language programs widened further as students reached high school. A 2017 study of dual-language immersion programs in Portland, Oregon, researchers also found that a greater share of ELs in dual-language classrooms became proficient in English by middle school, compared to their EL peers in English-only settings. A more recent study in Utah found similar benefits for ELs in dual-language programs that match their native languages.

ELs are more likely to reach English proficiency and be reclassified as former English learners when they have access to multilingual instruction.

Other studies show similar positive benefits for ELs in dual-language classrooms. A 2015 study in California found that ELs in dual-language programs did better on state literacy and math tests, concluding, “the test score growth rates of ELs in dual immersion far out-pace those of ELs in the other programs.” A 2021 North Carolina study also found academic benefits for ELs in dual-language programs—and some evidence that dual-language programs fostered more diverse learning environments.

How Does Dual-Language Immersion Improve ELs’ Language Learning?

To be sure, while researchers have shown that dual-language programs are better for ELs’ English acquisition, academic success, and bilingualism, they’re still teasing out exactly why they’re so effective. But the key mechanism appears to be that ELs who arrive at pre-K or kindergarten and begin the process of learning English generally do so by building upon the language skills they already have. That is, a child who speaks Spanish at home may not have very high levels of proficiency in English, but they do know something about how language generally works (because of what they know and can do in Spanish). They generally know how to build sentences, for instance, by using components such as nouns and verbs and descriptive words to convey meaning. So, unsurprisingly, they use that language knowledge—that they have developed by learning Spanish—to understand how English works. Not everything will be the same across the two languages, of course. But there are important commonalities, and those help ELs learn and succeed in both languages.

The speculation by researchers, then, is that an EL in a dual-language program deepens their understanding of their home language while simultaneously learning English. Immersion in both languages helps them build these cross-linguistic connections and, over time, stronger English skills and bilingualism than ELs enrolled in English-only settings.

Facts and Politics

Of course, knowing the facts about how schools can best help English learners will not resolve the political conflict on display in Arizona right now. The infighting between members of the state’s political leadership will inevitably be filtered (and perhaps resolved) through public debate and—apparently—the courts.

But it is still critical that these debates—as well as the decisions made further down the road—be anchored in the preponderance of solid data on what’s best for children’s linguistic and academic development. Otherwise the public will be stuck trying to decipher self-serving political rhetoric from known facts. Fortunately, the facts are relatively clear: dual-language immersion programs are the best way for English learners to learn English and succeed academically.