A valuable lesson about teacher ownership and its power to move a school forward was learned by the author as she worked with a professional development initiative on assessment: No matter how closely a district-level leader thinks she is connected to and trusted by a staff, the collective commitment, focus, and action of the teachers themselves is what ultimately has the greatest impact on student achievement. Teachers benefit from the support and guidance of a district-level professional development leader and a strong principal, but sustained professional learning by a staff focused on a single, schoolwide goal is what makes the difference for students. The author learned this lesson through her involvement with the teachers of Glenridge Elementary School in Clayton, MO. As the district's director of professional development and assessment, she was asked to facilitate a planning meeting on a teacher work day before school started that year. This article describes the author's experience and lessons she learned.