| Adolescent Language Minority (LM) learners in the U.S. face the daunting task of learning sophisticated content while simultaneously acquiring the language in which that content is taught. Yet, few studies have investigated growth in academic language skills in this population or evaluated instructional approaches to enhance them. In this thesis, I investigated two specific English skills considered to be important in LM learners' language development during early adolescence---morphological awareness (i.e., understanding of complex words as combinations of meaningful units) and vocabulary knowledge (i.e., knowledge of word meanings).;In the first study, I described the concurrent development of these two skills between fourth and seventh grade using longitudinal data on a cohort of Spanish-speaking LM learners (n = 90). Using latent growth modeling, I detected a strong relationship between rates of growth in the two skills, such that learners with rapid growth in morphological awareness also demonstrated rapid growth in vocabulary. Despite positive growth, the average LM learner remained far below national norms in vocabulary throughout this period.;In the second study, I evaluated the effects of an 18-week multicomponential vocabulary-morphology intervention on relational and syntactic aspects of morphological awareness for LM learners (n = 347) and native English speakers (n = 130) in sixth grade. In seven urban middle schools, intervention teachers and their students were matched to teachers providing the standard curriculum to comparable students. Using multilevel modeling, I found that the intervention improved both relational and syntactic aspects of morphological awareness for LM learners and improved relational, but not syntactic aspects for native English speakers. When compared to the estimate of annual growth in morphological awareness from the first study, these impacts are equivalent to seven months of additional growth.;Together, findings from the two studies suggest a reciprocal relationship between morphological awareness and vocabulary for LM learners, extending previous findings from research with monolinguals and informing a more elaborated developmental model of these processes for this population. While the persistent language deficiencies of LM learners highlight the need for intervention, findings also suggest that such intervention can result in practically meaningful gains. |
