Thirty exemplary 4th-grade teachers in six states were interviewed to determine the factors that influenced their development. The teachers cited three influences on their development: specific kinds of professional development, collegial support, and a sense of engaged autonomy. They valued professional development that provided a systematic way to observe and interpret students' work and actions. All the teachers mentioned a mentor or peer support network with which they could share ideas and reflect aloud. And all experienced engaged autonomy in which administrators allowed teachers freedom but still supported them.