Four organizations with promising practices in teacher Professional Growth & Support have significantly raised outcomes for low-income students. The charter management networks, Achievement First and Aspire Public Schools, and the two reform organizations, Teach Plus and Agile Mind, have successfully increased student achievement with a sustained focus on teaching effectiveness and capacity. As these organizations respond to the challenges of Common Core standards, invest heavily in teaching capacity through teacher leadership and collaborative planning time, and capitalize on assessment and evaluation data and technology, they exemplify best practices in Professional Growth & Support. They also reinforce what Education Resource Strategies (ERS) terms the Eight Principles of a Strategic Professional Growth & Support System which are presented here. The eight principles summarize ERS research and work with partner school systems and are the foundation for ERS' white paper, "A New Vision for Teacher Professional Growth & Support: Six Steps to a More Powerful School System Strategy" and related tools. This "Case Study of Agile Mind" is one of a series of four case studies. Each one describes the mission and background of the organization, strategic approaches to Professional Growth & Support, performance results, program costs, lessons learned, and next steps. "Agile Mind" is an example of a potentially cost effective way to bring high levels of expertise to bear in implementing Common Core Standards. Agile Mind's instructional guidance systems in math and science are designed to jump start the reform process and quickly grow teaching capacity, provide support, and improve achievement where school systems are most in need. [Other case studies in this series include: (1) Promising Practices in Professional Growth & Support: "Case Study of Aspire Public Schools" ED545133; (2) Promising Practices in Professional Growth & Support: "Case Study of Achievement First" ED545132; and (3) Promising Practices in Professional Growth & Support: "Case Study of Teach Plus" ED545134.]