Educational policies that impact second language (L2) learners—a rapidly-growing group—are often enacted without consulting relevant research. This review synthesized research regarding optimal conditions for L2 acquisition, facilitative L2 learner and teacher characteristics, and speed of L2 acquisition, from four bodies of work—foreign language education, child language research, sociocultural studies, and psycholinguistics—often overlooked by educators. Seventy-one peer-reviewed journal articles studying PK-12 L2 learners met inclusion criteria. Findings included: 1) Optimal conditions for L2 learners immersed in a majority-L2 society include strong home literacy practices, opportunities to use the L2 informally, well-implemented specially-designed L2 educational programs, and sufficient time devoted to L2 literacy instruction, whereas L2 learners with little L2 exposure require explicit instruction to master grammar; 2) L2 learners with strong L2 aptitude, motivation, and first language (L1) skills are more successful; 3) Effective L2 teachers demonstrate sufficient L2 proficiency, strong instructional skills, and proficiency in their students’ L1; 4) L2 learners require 3-7 years to reach L2 proficiency, with younger learners typically taking longer but more likely to achieve close-to-native results. These findings, even those most relevant to education, are not reflected in current US policy. Additional research is needed on the characteristics of successful or unsuccessful L2 learners and L2 teachers. Such research should attend systematically to the differences between L2 learning in maximal versus minimal input settings; whereas the psycholinguistic challenges of L2 learning might be common across settings, the sociocultural and interactional challenges and opportunities differ in ways that can massively impact outcomes.

Three common assumptions concerning bilingual children's language proficiency are: (1) their proficiency in two languages is usually unbalanced; (2) low socioeconomic status (SES) indicates low proficiency in both languages; and (3) encouraging parents to speak some societal language at home will promote its development. Examining the vocabulary scores of 282 bilingual Singaporean kindergartners (167 Chinese, 70 Malay, and 45 Tamil), the current study found that these young children were evenly divided among four language profiles: strong in ethnic language (Chinese, Malay or Tamil) or English, strong in both languages, or weak in both. Children with high proficiency in both languages were proportionally represented in the low, middle and high SES groups, demonstrating the achievability of strong vocabulary in two languages for children of different SES. However, low SES children were most at risk for low proficiency in both languages, although many achieved high proficiency in ethnic language or both. Middle and high SES children were most likely to demonstrate low ethnic language with high English proficiency. Children mostly exposed to one language from different sources generally showed strength in that language. Children exposed to both languages at home were most likely to show low proficiency in both languages, although plenty of children exposed to both languages developed high proficiency in English or both. These results affirm previous findings that SES and home language exposure influence bilingual children's proficiency. Implications include the importance of teachers assessing bilingual children's proficiency in both languages and collaborating with parents to develop bilingual children's vocabulary.

Because certain home language and literacy practices have been found to be beneficial to monolingual children's literacy development, we examine immigrant children's home language and literacy practices in different countries. Presenting findings from 92 post-2000 articles, we examine research into these practices, what factors influence their occurrence, how they influence immigrant children's development of literacy in the societal language, and what factors seem to moderate or mediate the effects of home literacy activities on societal-language literacy. We found that immigrant families engage in a wide variety of oral language and literacy activities at home, but that most of these practices have not been investigated in relation to immigrant children's literacy development. Book reading, the most-studied practice, seems to promote such development. Additional research is needed into the many factors that influence children's literacy development, including government policies and community context. In addition, researchers need to build on existing descriptive and correlational studies to design and implement innovative school curricula and family literacy programs that connect home and school practices and encourage parental involvement in the school.

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