This project studies the work of Lab School teachers providing one year of school-based professional development in “Cognitively Guided Instruction” to El Segundo Elementary Schools. The project focuses on the effort of Lab School teachers as facilitators of professional development, particularly the repeated cycles of planning, enacting, and reflecting upon their on-going practice. Researchers will take on the role of active participant-observers throughout this process. Any questions about this study should be directed to Angela Chan Turrou at achan@gseis.ucla.edu