This dissertation investigates how five Korean ESL (English as a Second Language) students in U.S. secondary schools develop academic writing while they navigate U.S. academic expectations and cultural norms. This qualitative study describes the experiences with academic writing practices and identity reconstruction as well as the relationship between writing and identity. The theoretical frameworks include sociocultural theory, writing and identity, and voice. Five Korean ESL students were recruited from U.S. secondary schools in Syracuse, New York. I employed five multiple case studies, in-depth interviews, and writing samples. Recursive and narrative analysis with the adaptations of Wortham's five types of cue were used for data analysis. Results demonstrate that ESL students as newcomers identified academic writing practices as a new genre of writing; therefore, their experiences with academic writing included the exploration of new cultural norms, values, and practices. The students shared similar challenges in academic writing and faced the issues of ascertaining teachers' expectations, elaborating upon their ideas for assigned topics, staying on topic, and formulating their voices. The students continuously reconstructed their identity as situated, multiple, paradoxical, hybrid, and nostalgic according to sociocultural contexts of writing and learning. This study illustrates that the natures of identities are intertwined with various genres of writing and that writing not only reflects writers' identities but also constructs their identities and multiple voices in and with writing practices. The ESL students' active socialization with teachers and peers nurtured their writing development and influenced their identity reconstruction. The rich and authentic descriptions contribute to a better understanding and teaching of ESL students' struggle, conflict, negotiation, choice and transformation in writing competence and identity reconstruction. Theoretical implications enlighten the different natures of L1 and L2 writing, the importance of English learners' cultural awareness, and the addition of new literacy to the fields of literacy and Second Language Acquisitions. Pedagogical implications illuminate authentic information about the writing needs of ESL students and rethinking the nature of explicit teaching. Methodological implications illustrate primary challenges and suggestions in relocating the students' multiple identities between spoken and written forms of language. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]