This dissertation builds on existing heritage language research (e.g., Albirini 2014, 2018; Benmamoun & Albirini 2018) and examines the complex and challenging practices of an understudied, marginalized, and stigmatized group of Muslim Arabic heritage-speaking children (MAHSC) and their immigrant families in the US. It argues that the diversity of the Muslim Arabic speaking community calls for using an interdisciplinary approach that investigates not only the unique linguistic performances of this group but also the perceptions, socialization practices, and identity representations that predict the status of their heritage language as they move across the private Islamic school domain, the home domain, and the Muslim community domain. Therefore, it uses Language Socialization (LS) (Ochs & Schieffelin 2011) from Linguistic Anthropology, Family Language Policy (FLP) (Spolsky 2004, 2012) from Child Language Acquisition and Policy Studies, and Accessibility & Accommodation (Garland-Thomson 2013; Titchkosky 2011) from Critical Disability Studies as theoretical frameworks for understanding whether and how these children take agentive roles in internalizing, adopting, and at times reversing the language policies mandated by the authoritative members of the domains they inhabit. Using a qualitative case study methodology, this dissertation answers the following research questions: 1) What do Muslim Arabic-speaking immigrant families and their MAHSC report regarding their heritage language (perceptions, practices, challenges, identities)? And what contributions, if any, do these reports add to current research on Arabic as a heritage language (AHL) in the US context? 2) What is the nature of the linguistic performance of MAHSC? What do these performances suggest in relation to AHL development? And what are possible mechanisms or explanations for the specific linguistic structures found in MAHSC's performances? And 3) What pedagogical implications does the study of second-generation MAHSC in the US suggest? The findings of this dissertation provide thick and detailed accounts of the impacts of the perceptions, practices, and challenges that the group under study engages in as they work against political, social, and educational pressures that marginalize rather than integrate them into American society because of their ethnic, racial, linguistic, and cultural backgrounds. Other findings revealed that children's digital literacy allowed them to become innovative language agents as they socialize with their extended family members through online gaming practices using a hybrid Arabic-English script. The interdisciplinary approach in my work offers new implications for advancing heritage language scholarship and Arabic heritage language instruction as it illuminates the power of children's agency in not only maintaining their heritage language but also presenting innovative heritage language tools that contribute to the development of their multiple identities. [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.]