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. The package includes a facilitator's guide with accompanying DVD and a participant's book of readings, handouts, and assignments. Participants in the Secondary Lenses on Learning program will expand their understanding of (1) the mathematical knowledge and dispositions that students need to be mathematically literate in today's world; and (2) the learning opportunities that need to be created to make significant mathematics accessible to all students. Over the course of the Secondary Lenses on Learning sessions, participants will: Explore concepts in middle and high school algebra Discuss readings that further illuminate the issues in each session Reflect on videotapes and written cases Examine various leadership tasks and responsibilities that contribute to an effective mathematics program The facilitator's component of the package includes detailed notes for each of the six sessions, video clips corresponding to individual sessions, numbered handouts, and sample documents for use with participants.