The Math Minds Initiative began with the goal to improve mathematics instruction at the elementary level, with an eye to all learners continuously extending their mathematical understanding. The project has integrated findings from cognitive sciences and six years of empirical data to develop both a teaching model (the RaPID model) and a framework for lesson observation and analysis. The model identifies essential elements of effective mathematics lessons, and the framework offers a lens for both teachers and researchers to attend to and analyze the interplay of resource, teacher, and learner in the context of individual lessons, with consideration of how they are woven into a broader learning trajectory. When project teachers have used the model/protocol in collaboration with a resource that clearly identifies and weaves together key mathematical ideas, we have seen a powerful impact on student learning. The chapter elaborates on the development of this framework, with particular attention to contemporary literature from the cognitive sciences that has oriented the project; it also includes a critical review