Heritage language development in Spanish-English-speaking preschoolers: Influences on growth and challenges in the first year of English-only instruction.

The sample was small and came from 26 children in Head Start programs in Los Angeles, a context with many Spanish speakers, so it may not apply to Spanish-English dual language learners in areas with less Spanish exposure. Children were followed for only one year, which may be too short to see later slowing or loss of Spanish. The sample had more girls than boys because the original study used snowball sampling, so gender findings may not be stable. The study did not measure language exposure and use, initial Spanish proficiency, maternal education or years in the US, so it cannot identify why children developed at different rates. The same model procedure was used for all outcomes, which may not be the best fit for each individual outcome.

Do not read the one-year growth as proof that Spanish will keep developing under English-only schooling. The study followed 26 children for one year in Los Angeles, and the authors note that longer exposure may still lead to slower Spanish development.