The Developing Algebra Resources for Teaching (DART) project has provided a series of professional development experiences in which teachers worked in collaborative teams on algebra topics they identified as challenging to teach or learn in an algebra I course. Twenty-one secondary mathematics teachers from seven O‘ahu schools worked in teams to develop algebra I modules, including the use of appropriate technology, to inform pedagogy and teacher knowledge beyond their textbook materials. The modules, referred to as educative curriculum materials (ECM), are intended to promote teacher learning in addition to student learning. In three whole-day professional development sessions conducted by CRDG’s Fay Zenigami, Hannah Slovin, Judy Olson, and Melfried Olson during the 2010–2011 school year, participants engaged in activities to deepen their own understanding of key algebra concepts and the Common Core State Standards for mathematics. They then identified topics related to proportional reasoning, algebraic reasoning, and rate of change and linearity as important yet difficult concepts for them to teach or for students to learn in a beginning algebra course. During the five-day summer 2011 professional development, the teachers organized into teams and closely examined their curriculum, other resource materials, and the Common Core State Standards for mathematical practices and content. They researched relevant literature, including technology and online resources, to develop materials for these topics. In addition to three whole-day professional development sessions during 2011–2012, teachers piloted activities to help their team further reflect on and refine their educative curriculum materials. Several teachers also observed others from their teams teach, which gave them feedback and insights on how their materials could be revised or enhanced.