The Secondary Lenses on Learning professional development materials were designed to support the efforts of site-based mathematics improvement teams of mathematics leaders to advance middle and high school students’ mathematics achievement. Participants in the Secondary Lenses on Learning program will expand their understanding of the mathematical knowledge and dispositions that students need to be mathematically literate in today’s world and the learning opportunities that need to be created to make significant mathematics accessible to all students. The Secondary Lenses on Learning Participant Book features detailed notes for each of the six sessions, corresponding readings, handouts, and assignments. Over the course of the Secondary Lenses on Learning sessions, participants will: explore concepts in middle and high school algebra; discuss readings that illuminate the issues in each session; reflect on filmed material and written cases; and, examine various leadership tasks and responsibilities that contribute to an effective mathematics program. Multiple copies of the participant books are available separately to accommodate your group’s specific needs. For the facilitator, the Secondary Lenses on Learning comprehensive package includes one participant book, one facilitator’s guide, and an accompanying DVD with segments that correlate to individual sessions.