Responsiveness to students’ sense-making is a challenging improvisational teaching practice. This study utilized a design-based approach to co-design tools and mentoring routines in support of two novice elementary teachers in their classrooms in order to improve their responsiveness. I spent one week with each teacher as she taught a mini-science unit, provided opportunities to students to engage in sense-making, and worked and reflected on her own responsiveness. Findings indicate that the tools, both conceptual and practice-based, as well as the mentoring routines, functioned best in response to the teachers’ needs. This suggests that understanding the particular problems of practice a teacher experiences is important when scaffolding professional learning experiences to target a given skill.