An important issue that parents and teachers ask about is whether parents of DLLs should use the home language with children exclusively or try to encourage more English use. Research and experience have established that children can learn more than one language, either simultaneously or sequentially, with no adverse effects.
In fact, in addition to the social and cultural benefits, there are potential cognitive advantages to growing up bilingual. Yet many parents—and teachers—assume it is common sense that speaking more English at home will promote higher levels of English proficiency for children. Correlational studies do tend to corroborate these intuitions; use of any language at home is positively associated with children’s learning outcomes in that language and negatively associated with outcomes in the other language. But findings are mixed: one study found that increased use of English by Spanish-speaking mothers did not accelerate English growth by children—but it did decelerate Spanish vocabulary growth