Educators caution that not all dual-language programs are equally good. If a program is not run properly, they say, the pace might be catered to native English speakers, so content in English becomes more difficult and content in the other language is too easy. And even at well-run programs, hiring qualified teachers can be a challenge.
Sean Reardon, a professor at Stanford University’s Graduate School of Education who has researched dual-language programs, said there might also be a difference depending on what two languages are being taught. While Spanish and English are phonologically similar, sharing an alphabet and many sounds, character-based languages like Chinese are quite different, he said, and that might make it more difficult for students to follow along.
“I don’t think there’s one answer in the research, is dual-language immersion good or bad,” Professor Reardon said. “I think it might well depend on what the other language is relative to your home language.”
That said, he added, there is only so much that can be measured.
“There is great value in having a kid grow up to be bilingual, and even if your kid didn’t do quite as well on the standardized math test, maybe that’s worth it,” he said. “In the end, they come out with this whole extra skill they wouldn’t otherwise have had.”