This design research study describes how one mentor teacher-teacher candidate dyad co-learned to promote student engagement and participation through using a "Collaborative Learning Structure" (CLS) tool that we are developing. We share how the dyad used the CLS, with support from a professional development facilitator and fellow teachers, to better identify student assets (a critical component of promoting student engagement and participation). Our analysis demonstrates that (1) co-noticing is a productive means of supporting dyad co-learning to promote student engagement and participation and (2) teachers need to co-learn across time while using tools supportive of their learning. We discuss implications for how to support teachers in promoting student engagement and participation. [For the complete proceedings, see ED658295.]