If we want talented young teachers to develop the capacity to get students excited about high-quality science, technology, engineering, and mathematics (STEM) learning, we must develop a network of STEM teachers who can support teachers in their continued learning about their work and enable them to collaborate with others. If we want teachers to stay in the profession long enough to develop that capacity, we need to support them in developing the agency and autonomy to drive their own professional growth and become stewards of their profession. This kind of agency and autonomy is crucial for making teaching a rewarding and viable career option over the long haul, and attracting and retaining the best and the brightest to the profession.