Students tend to perform at the academic level expected of them. Although most expectation research has centered investigation of decontextualized teacher-student dyads to understand whether students behaviorally confirm their teacher's expectation, we now know that expectations operate at whole-group or system levels. Since underestimation is more common within historically marginalized learning communities, these student groups can experience comprehensive systems of underestimation at the level of the institution, with lifelong consequences for success and well-being. While intervening in such systems is possible (e.g., changing beliefs or practices to ensure over-estimation), it remains difficult because researchers do not yet understand how academic expectations are constructed or what governs the process. This is essential knowledge for generating more equitable expectation systems. Academic expectations constitute a complex and dynamic system. However, methodologies traditionally used to investigate them have collectively assumed otherwise, likely masking the pervasiveness of underestimation in marginalized settings. In this ethnographic case study I examine expectation co-construction in one 11th grade classroom serving marginalized students. Analyzing over seven hours of classroom discourse and fieldnotes across a five week span, participant recall interviews, learning artifacts, and archival data, I investigate three interdependent system facets: teachers' and students' expectation-related discourse; sociocultural inputs operating at multiple levels; and the emerging role identities of teachers and three focal students in relation to expectations. I describe and map an integrated network of 27 emerging expectations, and explain the "how" and "why" of their situated co-construction by members of the learning community. I argue that individuals' awareness of their own contributions to the everyday behaviors, beliefs, and discourse that construct and reproduce underestimated expectations is critical to disrupting such systems. This study offers practitioners and researchers an adaptable methodology to build this awareness and inform subsequent interventions. [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.]