Student-teaching field placements play an important role in preparing teacher candidates, many of whom rate the practice as the most authentic and relevant learning experience associated with their teacher-education programs. As a part of these field experiences, teacher candidates have opportunities to learn instructional and class management strategies from mentor teachers. These placements also provide opportunities for teacher candidates to connect methodological and theoretical content taught at the university with actual practices at K-12 public schools. But what effects do field placements have on teacher performance? To help build a research base in the field of student-teacher development, this study examines how a lesson-study approach to student-teaching supervision, Shared Mentoring in Instructional Learning Environments (SMILE), affects teacher candidates' achievement on the edTPA, a performance-based assessment for teachers. SMILE established professional learning communities (PLCs) with two to three teacher candidates who are working at one site with students of similar ages (elementary schools), their mentor teachers, and a university supervisor. Thirty participants (teacher candidates) in the SMILE cohort were assigned to a mentor teacher in one of eight elementary schools. The comparison group included 30 participants (teacher candidates), each of whom experienced the traditional model of supervision by being assigned to a mentor teacher without SMILE PLCs at school sites. Four university liaisons worked with the 30 teacher candidates in the SMILE program and an additional four university supervisors implemented the traditional model of supervision with that cohort. Upon completion and submission of edTPAs, all participants were interviewed in focus groups. Findings show a trend toward higher quality planning for diverse learning needs and assessment analysis among teacher candidates who engaged in the SMILE model than among teacher candidates from the traditional cohort.