For the last decade, much of the work of California school administrators has been shaped by the accountability of the No Child Left Behind Act. Now as they stand at the precipice of Common Core Standards and next generation assessments, it is important to reflect on the proficiency educators have attained in using data to improve instruction and student outcomes. What lessons are of value for 21st century teaching and learning and beyond? At the end of one accountability system and the beginning of a new one, it is useful to review research-based data analysis practices to determine how to best provide continued alignment between teaching and learning for the next decade.