Teaching residencies offer opportunities for sustained support within schools as a liminal space for novice teachers, and school-based mentor teachers significantly impact residency outcomes. Mentoring improves when mentors have clear expectations for their role and support for meeting those expectations. This mixed-method case study investigates the effects of a model for mentor training, its impact on residents' learning, and the perceptions of mentors and residents regarding support provided. Quantitative findings showed a statistically significant difference in growth for residents whose mentors were trained in the Gradual Increase of Responsibility mentoring model compared with those who were not. Qualitative analysis offers support for differentiated use of the mentoring moves of modeling, recommending, questioning, affirming, and praising (with this sequence expressing de-escalating levels of support). Findings suggest that when mentoring varies based on residents' differing and changing skill levels, teaching improves. Centering dialogue in mentor/resident interactions supports change and growth.