This article, based on a longitudinal interview study of 50 new teachers in Massachusetts, presents respondents' reasons for staying in their schools, moving to new schools, or leaving public school teaching within their first 3 years of teaching. Although the respondents' prior career orientations, financial situations, and preparation played a role in their career decisions, their experiences at the school sites were central in influencing their decisions. Teachers who felt successful with students and whose schools were organized to support them in their teaching--providing collegial interaction, opportunities for growth, appropriate assignments, adequate resources, and schoolwide structures supporting student learning--were more likely to stay in their schools, and in teaching, than teachers whose whose schools were not so organized. (Contains 3 tables, 1 figure and 7 notes.)