This dissertation provides a model for reconsidering student agency in educational spaces and specifically in self-placement practices. Employing a Cooperative Inquiry framework in which students were included in the research process, this project sought to understand the experience of incoming students at a larger research-intensive institution who engaged in a variation of self-placement in writing classes, commonly referred to as Directed Self-Placement (DSP). Through partnering with students, the results of this study suggest that what others have speculated (Ketai, 2016; Toth, 2018) is largely correct: student agency in self-placement does not lead to a natural sorting of students by their writing ability or needs. Instead, the findings from this project suggest that students choose classes based on a nexus of factors, some of which are deeply personal, like their cultural background or beliefs of self, while others are endemic to American educational culture, like the authority of standardized testing or the power of Standard Language Ideologies. Therefore, this project provides an ecological understanding of agency, which seeks to acknowledge multiple definitions of agency and the lived experiences of students. To build this new model of agency, this study presents multiple forms of data collected in consultation with students including surveys, focus groups led by undergraduate researchers, and one-on-one interviews conducted overtime. Taken together, these data points help to craft revealing narratives about the filters, as I refer to them, through which students process their agentive action while engaging in choice around their placement. Specifically, no matter the identity of the student, the choice students engage in is not neutral or easily negotiated. The findings suggest that all students, regardless of their background, filter their choice in a class through their past educational experiences, deferring their authority to past assessments. Further, while research that has quantitatively analyzed DSP instruments has indicated that DSP instruments can disproportionately place minoritized students in basic writing courses (Kosiewicz & Ngo, 2020; Tinkle et al., 2022), this project provides a holistic view of how a cohort of incoming students may individually differ in their choice-making processes, with special attention to student identity and positionality. Specifically, this dissertation finds that the more historically subjugated identities a student has (multilingual, first generation, person of color, etc.), the more complex their negotiation of choice becomes. Students who are from multiply marginalized identities more often view their choice through the lens of Standard Language Ideologies (SLIs), cultural understandings of education, and socioeconomic realities that shape their view of higher education. In naming the differences in students' choice making processes and their use of agency, this project works to understand how students from historically disenfranchised identities have to be more savvy and more contextually considerate than their peers in their agentive action. As the first of its kind to employ methodologies that center student experience in self-placement, this study directly refutes the belief that providing students with choice will automatically lead to equitable outcomes and complicates the field's notion of agency and provides a new model for understanding student agency. As placement serves as a gateway experience for all students and self-placement practices are increasingly taken up in the pursuit of equity, this dissertation provides important insight into how students filter their decision-making process and how administrators, or writing programs and placement in general, should reconsider and employ an ecological model of agency. [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.]