How do some school districts not only attain excellence but sustain it over time in the face of remarkable challenges? Two districts--Blue Valley School District in Overland Park, Kansas, and Kildeer Countryside Community Consolidated School District 96 in Buffalo Grove, Illinois--have managed to do just that by functioning as professional learning communities. These districts have achieved remarkable results over an extended period of time despite changes in principal, teacher, and student demographics. In these districts, the keys to success have been the creation of greater clarity and coherence with a single-minded focus on implementation of professional learning communities districtwide. This article describes how Blue Valley School District and Kildeer Countryside Community Consolidated School District implemented the professional learning communities.