The Lead Teacher Program (LTP) is organized by Beyond Benign, an institution that promotes green chemistry principles and sustainability in education. LTP trains K-12 teachers to run workshops in their own communities across the US and Canada. This research project aimed to study the culture among K-12 science teachers in LTP and how they share new beliefs, knowledge, and skills in organized settings like workshops and in ongoing ways with peer teachers in their communities. Our research team focused on Pedagogical Content Knowledge (PCK) as the subset of teacher expertise that captures how they teach in content-specific ways. As a case study, we followed a group of teacher leaders working in LTP to better understand how these practices were transformed and shared between peer teachers. My three main research questions were: (1) How does PCK transfer and transform between K-12 teachers in an empowering, peer-led community? (2) What effects does teacher empowerment have on their classroom teaching practices and PCK? (3) Which organized program activities and other community interactions support teachers' sharing and development of PCK? I investigated these questions through a mixed methods approach that considered descriptive data about teachers' knowledge of PCK related to green chemistry, qualitative classroom observations, and personal interviews with teachers. Studying a scalable, geographically-diverse, peer-led, sustainable, and innovative community focused on green chemistry education can help us understand better how to create and maintain similar educational communities in a wide variety of contexts. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]