This longitudinal study examined morphosyntactic development in the heritage Arabic-L1 and English-L2 of first-generation Syrian refugee children (mean age = 9.5; range = 6–13) within their first three years in Canada. Morphosyntactic abilities were measured using sentence repetition tasks (SRTs) in English and Syrian Arabic that included diverse morphosyntactic structures. Direct measures of verbal and non-verbal cognitive skills were obtained, and a parent questionnaire provided the age at L2 acquisition onset (AOA) and input variables. We found the following: Dominance in the L1 was evident at both time periods, regardless of AOA, and growth in bilingual abilities was found over time. Cognitive skills accounted for substantial variance in SRT scores in both languages and at both times. An older AOA was associated with superior SRT scores at Time−1 for both languages, but at Time-2, older AOA only contributed to superior SRT scores in Arabic. Using the L2 with siblings gave a boost to English at Time−1 but had a negative effect on Arabic at Time-2. We conclude that first-generation children show strong heritage-L1 maintenance early on, and individual differences in cognitive skills have stable effects on morphosyntax in both languages over time, but age and input factors have differential effects on each language and over time.

Although age of acquisition (AoA) is frequently used when examining the endpoint of second language (L2) learning, it is rarely used to examine the initial phases of L2 acquisition. The present study provided a unique look at the role of AoA in early language and literacy acquisition in the L2 by a priori selecting two groups of Arabic-English speakers based on their ages, 6–8-year-olds (N = 43) and 9–13-year-olds (N = 53). These Syrian refugees were matched on English experience, having immigrated to Canada and having learned English for two years or less. Raw scores on language and literacy measures were compared across groups. The older group had higher scores on all first language (L1) variables. The groups did not differ on most L2 variables except for English word reading. Additionally, L1 and L2 variables were examined in relation to English word and pseudoword reading with different patterns of relations found for the two groups. For the younger group, phonological awareness and vocabulary were related to reading, while for the older group phonological awareness and morphological awareness were key predictors. These finding points to the unique relations among age, age of acquisition, L1 skills, and L2 language and literacy skills.