This article presents a case study of how educators in one northeastern school district participated in school-based learning through lesson study (LS). Using a sociocultural perspective on teachers' learning, I compared the participation of educators who were new to lesson study ("LS novices") with those who had more experience with the practice ("LS experienced practitioners"). Consistent with prior research, I discovered that LS novices focused primarily on learning the routine and on the novelty of observing instruction. LS experienced practitioners, in contrast, were comfortable with the routine and thus concentrated instead on how they elicited students' thinking. I discuss how educators might progress from having a less developed to a more developed understanding of lesson study, and how supports such as routine participation and interactions with knowledgeable experts might help educators develop their understanding and application of lesson study over time.