Although the structural basis of language acquisition is very much in place by the time children start school, language acquisition and consolidation continue during the school-age period (Berman, 2004). Literacy involves exposure to formal and decontextualized uses of languages and a variety of registers. Its consolidating effects appear to involve several linguistic domains simultaneously, fostering vocabulary, semantic, syntactic and pragmatic growth (Montrul and Armstrong, 2024). Furthermore, literacy enhances children's reflections on formal aspects of language. The question of how literacy and text exposure contribute to linguistic development is fundamental for understanding heritage language growth, as this process can be hampered under conditions of reduced input in childhood and beyond. Heritage language exposure and use typically diminish substantially when bilingual children start school in the majority language (Montrul, 2016), and a shift toward the majority language is often inevitable during the school years, regardless of education program (Paradis et al., 2021). Under these conditions, literacy in the heritage language is very likely to play a fundamental role in its development and maintenance (Bayram et al., 2017; Torregrossa et al., 2023b).

While much research has documented the effectiveness of dual language programs for bilingual children's academic achievement and majority language skills (Paradis et al., 2021), less attention has been paid to their influence on specific linguistic features of children's heritage language skills (Gathercole and Thomas, 2009). This line of inquiry is particularly valuable, as the acquisition of different linguistic phenomena may vary in their sensitivity to language and literacy exposure (Tsimpli, 2014). Furthermore, school-based programs that teach heritage languages often show substantial variation in the number of hours dedicated to the majority or heritage language and in the degree of integration between the majority and heritage language during classroom activities. Therefore, there is a critical need to examine variation across heritage language education programs in terms of literacy instruction and to investigate how such variation affects children's acquisition outcomes in the heritage language. Complementary, informal heritage-language classes outside of regular school settings often operate two-to-three hours weekly, raising the question of whether this limited exposure is sufficient to have a significant impact on children's heritage language abilities. Finally, home literacy practices, such as parent-child interactions during book reading, also vary considerably across families.

We know relatively little about how literacy exposure and other language-exposure variables within the family and community build on or interact with each other in determining heritage language acquisition outcomes (Paradis, 2023). Parental attitudes toward bilingualism may lead to the suppression of the home language, often guided by the mistaken belief that maintaining the heritage language hinders success in school (Hurtado and Vega, 2004; Rosa, 2019; Oller et al., 2007). This view contrasts with evidence showing that students who are literate in their heritage language(s) have stronger academic achievement in the school language than those who are not (MacSwan et al., 2017; Umansky and Reardon, 2014), and that there is interdependence between languages in biliteracy and bilingual development (Paradis et al., 2021; Torregrossa et al., 2023a). Furthermore, whether literacy exposure in the majority language has positive, neutral or negative effects on heritage language abilities remains underexplored.

Many of these questions are addressed in the present collection, which features studies of school-age heritage speakers of Spanish, Portuguese, Mandarin and Romanian in different majority language contexts (Australia, Canada, Germany, Switzerland and the United States). These children receive literacy instruction informally at home, in after-school community heritage language classes, or in bilingual schools. Despite differences in empirical focus, theoretical frameworks and research methodologies, all studies converge on the finding that literacy exposure in the heritage language contributes positively to its maintenance and development in school-age children. At the same time, the findings reveal important interactions between parental attitudes, literacy strategies, and educational program types, highlighting their combined impact on specific areas of grammatical development as well as on both receptive and productive language skills.

Escudero et al. measured linguistic proficiency (vocabulary, listening, speaking, literacy/numeracy) to document the success of a Spanish heritage language program for pre-school children in Australia. Three studies focused on linguistic structures that are typically early acquired by children but require sustained input for eventual mastery. Pirvulescu and Hill, and Austin et al. examined the development of clitic pronouns in Romanian and in Spanish, respectively, while Daskalaki et al. investigated vocabulary and wh-question production in Mandarin-speaking children. Torregrossa et al., and Armstrong and Montrul presented data on later-acquired structures in Portuguese and Spanish. Although children who speak Spanish or Romanian as a heritage language seem to develop knowledge of clitics, school-age speakers still show developmental errors typically found in younger monolinguals, such as clitic omission (Pirvulescu and Hill). Gender errors with clitics also persist among Spanish-speaking children attending dual immersion programs alongside L2 learners (Austin et al.) and among Romanian heritage language children. Literacy in Romanian predicted higher accuracy in clitic production, while it did not influence clitic comprehension. In a comprehension task, Austin et al. found that heritage language children were not more accurate in clitic comprehension than L2 learners attending the same bilingual school.

In production tasks involving complex structures, both Torregrossa et al., and Armstrong and Montrul showed significant literacy effects in Portuguese and Spanish, suggesting that literacy plays a significant role in the development and consolidation of these structures. There seems to be an intriguing interplay between early- vs. late-acquired structures, comprehension and production, and literacy exposure. Unsurprisingly, the studies that compared groups of heritage language children receiving literacy instruction in different contexts (home, heritage language program/community school, bilingual education)—Daskalaki et al. and Armstrong and Montrul—confirm that the greatest heritage language development and maintenance occur in programs that provide more instructional contact hours per week in the heritage language. Finally, both Daskalaki et al. and Costa Wätzold and Melo-Pfeifer report that parental attitudes and home language strategies, including formal and informal literacy activities carried out dynamically in both the heritage and majority languages, contribute significantly to heritage language development and maintenance.