Physics classrooms, from high school through graduate school, chronically enroll far too few women, people of color, English language learners, and low-income students. Research suggests students' science identity functions as a strong indicator for their continued pursuit of physics coursework and careers. Further research indicates students' classroom experiences significantly shape their science identity. Rooted in situated learning as the theoretical frame, recognition of performance and competence in a community of practice of physicists functions to operationalize science identity. This action-research study explored the interaction between the decisions I made while implementing inquiry-based modeling activities in AP Physics 1 and students' science identities. This study specifically focused on full class, post-lab discussions where students developed mathematical models of physical phenomenon. In preparing for and managing these full class discussions, I made a multitude of pedagogical decisions that shaped opportunities for recognition of students' competence in and performance of expertise in AP Physics 1 content and skills. Through systematic reflection as a practitioner and analysis of classroom dynamics, this study revealed two overarching themes of tensions in my decisions between pedagogical priorities in these discussions. First, whether and how to best implement scaffolding to develop student expertise in both physics content and scientific practices. Specifically, decisions I made within this theme navigated: 1) how to design social scaffolds to shape classroom interactional norms, 2) how to manage analytical scaffolds, including IRE cycles, 3) when to emphasize skills or content during their integration, 4) how to reframe student inaccuracies as an opportunity for competence. The second theme of decisions I made navigated how to structure opportunities for student engagement to encourage all students to experience a sense of agency through meaningful recognition. Specifically, decisions within this theme fell into two tensions: 1) how to structure engagement in the discussion through explicit or fluid roles, 2) how to increase students' agency in choosing when and how to participate while also encouraging equitable participation from all students. Awareness of, and attention to, these tensions offers implications for best practices during modeling activities in introductory physics classrooms. Broadly, these implications for practice point toward making my decisions about supporting students' expertise and engagement more explicit to students to increase their agency and competence in pedagogical goals. First, explicitly teaching how mathematically modeling physical phenomena at the beginning of a unit fits within the broader modeling cycle. Second, explicitly naming hegemonic barriers to students' matriculation so as to build classroom norms that strengthen students' resilience. Beyond implications for practice, this study offers theoretical insights that may guide future research in modeling and science identity. [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.]