Green chemistry developed historically from twelve industrial principles for research chemists. Recently, interest has grown to begin introducing these principles in science classrooms even at the secondary and pre-secondary school levels. However, teachers must do significant work to adapt and translate green chemistry from the industrial or manufacturing perspective into one more appropriate to students at younger ages. This research project explores how a group of current teachers in the US and Canada have been developing their language and understanding of green chemistry through Beyond Benign's Lead Teacher Program. Transcripts from phone interviews with program participants are analyzed to propose a classroom-based definition of green chemistry and its justification as an approach at the secondary and pre-secondary school levels. This pedagogical understanding provides a foundation to solidify green chemistry as a standard practice in science education. Then classroom observations and case studies of four teachers are developed into a framework for green chemistry education at the K-12 level.