Since the passage of No Child Left Behind nearly twenty years ago, teachers' and students' educational experiences have been largely shaped by the high-stakes accountability system. The consequences of high-stakes accountability can be exacerbated in bilingual settings, because in these contexts often contradictory assessment policies and language policies interact. This dissertation study examines how bilingual teachers engage with a transitional bilingual policy while balancing the demands of monolingual high-stakes assessments in ways that contribute to advocacy on behalf of their bilingual learners. Applying a Figured Worlds theoretical framing (Holland, Lachicotte, Skinner & Cain, 1998) in a vertical comparison case study design (Bartlett & Vavrus, 2017), the author explores three bilingual teacher's policy work from an agency lens. Findings reveal that teachers' agentive policy work takes multiple forms, some less visible than others, and that identity, ideology and context all play significant roles in mediating teachers' policy actions. This study carries implications for teachers, teacher educators, educational researchers, school leaders and policy-makers in their efforts to improve equitable educational experiences for bilingual learners in the context of high-stakes accountability. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]