In this article, Anthony Bryk, Heather Harding, and Sharon Greenberg report on a roundtable jointly sponsored by Teach For America and the Carnegie Foundation for the Advancement of Teaching. The authors brought together a group of scholars and practitioners with a broad range of perspectives and asked them to explore several questions related to the emerging national narrative on effective teachers: What is an effective teacher? How do we leverage this moment of enormous energy in producing more effective teaching to advance meaningful improvements at scale? Where are the current sites of success? What can we learn from what is working? The article is organized around the edited transcript of the roundtable discussion and is supplemented by author commentaries. The authors seek to illuminate and reimagine the current "nonsystem" in order to accelerate progress toward a wholly new approach to developing the teaching force our nation and our children need. (Contains 11 notes.)