Background/Context: Student teaching represents a critical component of most teacher education programs. However, there is significant variation both in the contextual factors that preservice teachers (PSTs) encounter in their field placements and in the ways that teacher educators mediate PSTs' learning in relation to those placements. In this article, Cultural Historical Activity Theory (CHAT) provides the theoretical framework for considering this complex endeavor. Purpose/Objective: This article unpacks a salient excerpt from an interview that was conducted as part of a larger qualitative study focused on situating student teaching in urban high-needs schools. The authors use one participant's description of her student teaching experience as a starting point for mapping the contextual factors that appeared to mediate her practice--and her learning about practice--in her placement. The authors then consider how teacher educators might have better supported the student teacher, thereby enhancing her own and her students' learning. Conclusions/Recommendations: The authors conclude that conceptualizing student teaching through an activity system lens affords teacher educators the opportunity to think about student teaching in more contextualized ways, to set clearer, context-specific learning goals, and to strategically re-mediate PSTs' learning in relation to those goals. Implications include recommendations for deepening collaboration with cooperating teachers and otherwise working to build coherence across university-based and field-based settings in an era of high-stakes accountability.