Emerging research finds connections between teacher candidates' student teaching placements and their future career paths and effectiveness. Yet relatively little is known about the factors that influence these placements and how teacher education programs (TEPs) and K-12 school systems match teacher candidates to mentor teachers. In our study of this process in Washington state, we find that TEPs and K-12 systems share overarching goals related to successful student teacher placements and developing a highly effective teacher workforce. However, distinct accountabilities and day-to-day demands also sometimes lead them to prioritize other objectives. In addition, we identified informational asymmetries, which left TEPs questioning how mentor teachers were selected, and districts and schools with limited information with which to make intentional matches between teacher candidates and mentor teachers. The findings from this study inform both practice and research in teacher education and human resources. First, they illuminate practices that appear to contribute to informational gaps and institutional disadvantages in the placement of student teachers. Additionally, they raise questions about what constitutes an effective mentor teacher and provide researchers and policymakers with better insight into the professional realities of teacher educators and K-12 educators, as well as those of district human resource (HR) coordinators, which is important given their differing accountabilities and distinctive positionings in the education of teacher candidates.