To refocus its professional development plan, Chaska Middle School East (Minnesota) looked at where student achievement was lagging. Using the Killion back-mapping model, a student-focused, data-driven, multi-step process by which teachers gather and study student data to determine where professional growth, development, or training is most needed, the school's professional development team--made up of teachers, the professional development coordinator, the district assessment coordinator, and the principal--designed professional development plans that aligned with their needs. Holes in the data prompted the adoption of the Internet-enabled Measures of Academic Progress (MAP), a series of three different tests in reading, language arts, and math that can be tailored to each student's specific needs. Combining the Killion model with MAP testing is significantly affecting the professional development program in Chaska. Curriculum materials, professional development training, and teaching strategies are more purposefully aligned to increase inferential reading comprehension. Testing will be used periodically to gauge the effectiveness of this realignment. Now, more than ever, Chaska teachers are better prepared to make a real difference for each student. (Contains 1 figure.)