Good teaching occurs when educators on teams are involved in a cycle in which they analyze data, determine student and adult learning goals based on that analysis, design joint lessons that use evidence-based strategies, have access to coaches for support in improving their classroom instruction, and then assess how their learning and teamwork affects student achievement. Recognizing the need to ensure high-quality professional learning for every educator, National Staff Development Council (NSDC) is advocating for a powerful new definition of professional development based on this model of continuous improvement. The new definition calls for every educator to engage in professional learning at the school as part of the workday. Professional learning should tap the expertise of educators in the school and at the district office, with support from universities and other external experts who help local educators address needs specific to their students and school improvement goals. When schools and school systems adopt the definition and alter their own understanding of high-quality professional learning, teacher practices and student achievement will begin to change. (Contains 1 table.)