The definition of literacy is constantly changing and expanding. A sociocultural view of Literacy considers literacy to be multiple, multimodal, and multilingual as situated in and across the social and cultural contexts. As technology, new media and social network has reformed many aspects of writing, they provide ELLs (English language learners) with supports and resources while at the same time raising new challenges. Although adolescent ELLs are a very active group that use technology, new media and social network, they remain an under-represented group in the L2 writing research; and very little is known about the social practices of these writers as they use technology and digital media to develop and maintain social relationships in the local and global contexts. It is important to examine their writing practices across the school, home, and community contexts as they are immersed in technology and digital literacy practices. In the light of a sociocultural and socio-critical view of literacy, I conduct the year-long ethnographically oriented multiple case studies of 4 high school students in a Western urban community in the United States in order to understand their school-sponsored and self-sponsored writing practices in the digital age; and to examine the relationship, potential link and possible gaps between these practices. I observe their in-class writings in a 6-week period, and throughout the year collect multiple sources of data from formal and informal interviews, survey, field notes, literacy log, writing samples, and their self-select writing artifacts. I also become a member of their web-based social networks and gain access to their writings on the web logs, forums, Facebook, and Twitter. In the inductive analysis of the data, I notice important and recurrent themes such as the writers' identity construction and negotiation, socialization, and language use. Findings reveal that while school-sponsored writings provide opportunities for both individual and collaborative writings and chances of sharing, students consider certain tasks more meaningful than others. As the four participants in this study engaged in a wide range of self-sponsored out-of-school literacy practices, every participant was unique in their choice of the types of literacy practices, their preferences for the medium of composing, the sharing of their writings, and the language choices for their writings. One important findings is that their choices of languages, code meshing, and frequent use of internet and urban slangs showed their eagerness to belong to an adolescent social circle which valued their ethnicity, gender, linguistic heritage, and popular cultural literacies. As they consider English "extremely important", they all value their heritage languages as part of their identity construction. The links between the school and self-sponsored writings are obvious. There is overlapping in topics, genres, recurrent themes, language uses, sociocultural experiences that feed the writings. The writing processes are also impacted by each other. As for the gaps, while self-sponsored writings provide more chances for sharing and expressing, they are more informal and sometimes even fragmentary. I argue that while it is important to acknowledge the richness of students' self-sponsored writings and the potentials of technology and social networks, educators should not over-romanticize these writings or the role of technology, as they may also become distractions. It is also important to focus on the meaningful connections and possible gaps rather than drawing a boundary between the in-school and out-of-school literacy. This study offers new understandings and insights into the writing practices of the English language learners in the digital age. It calls for future longitudinal studies that connect the secondary and post-secondary education which will provide more complete descriptions and useful information on how they could be better prepared for college writing classes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]