What kinds of teacher collaboration are most likely to improve what teachers--and, ultimately, students--learn during their time in school? This study looks within and across different collaborative activities that occurred among one teacher team. Observational data analyzed through a sociocultural theoretical framework suggest how the structure and intended focus of collaborative activity can influence (1) how often and how concretely teachers discuss their teaching with colleagues; (2) which aspects of schooling collaboration will address; and (3) what opportunities for teacher learning are afforded and constrained. Intentionally focusing and structuring teachers' collaborative activity can improve its impact on schooling. (Contains 4 tables and 1 figure.)