The author, an executive director of Assessment and Accountability for the Poway Unified School District, relates how their school district implemented an assessment program with practical applications to teaching and learning. Rather than being yet another burden on teachers or a local report card on schools, the district's goal was to define and implement an assessment system that complemented the state's summative testing program--one that teachers and students could embrace and apply to focus and guide their work. So, in 2001, they selected a computerized adaptive test that measured individual student growth over time and delivered immediate results. The first schools to fully embrace the new assessment--some of their lowest socioeconomic (Title I) schools--quickly became some of their highest performing academically. They now have a new culture of collaboration and involvement around the use of data, with students and teachers working together to set and achieve growth targets, and teachers collaborating on best practices based on their students' test data.