This dissertation examines the academic and social goals that three second-grade English language learners in a U.S. urban school bring to their blog-mediated academic writing practices, and the interrelated nature of those goals. This study aims to bridge the dichotomy between approaches to studying computer-mediated language and literacy development that are oriented toward academic goals inside school, and those that are oriented toward social goals outside school. The study also aims to investigate connections between language use and language development by highlighting linguistic features of semiotic choices that the students made for their texts. This builds upon recent research studies of literacy practices that focus only on situated uses of literacy in various social and cultural contexts (Christie & Martin, 2007). In this study, learning is defined as appropriation and language is defined as a semiotic system, from sociocultural perspectives that capture the transformative nature of tool-mediated practices (Bakhtin, 1981; Halliday, 1985; Kress, 1998; Vygotsky, 1978). Ethnographic data collected over the course of a year include students’ texts, blog comments, videotaped classroom interactions, interviews, instructional materials, and school documents. Analysis of the data examines student goals, semiotic choices employed by the students, and roles adopted by the students, in the social processes of learning academic genres. Systemic functional linguistics is used to analyze register variables across texts and blogging comments, to examine changes in the students’ uses of linguistic resources. The findings demonstrate that students appropriate blogging for both academic and social goals, and compose their texts by drawing on linguistic features appropriate for goals related to the audiences reading their blog posts. Writing for meaningful goals and for wider audiences encourages ELLs to become more invested in learning, and to use linguistic patterns in context-dependent ways. The study concludes with a discussion of the significance of social goals in developing critical academic literacies (Gebhard, Harman, & Seger, 2007), and implications for K-12 educators who are attempting to open up curricular spaces in which all stakeholders collaboratively work toward transformative learning experiences for ELLs (Willett & Rosenberger, 2005).