This report examines three types of professional development supports often provided by early childhood programs: (1) teacher training, (2) teacher coaching, and (3) common planning or "prep" time. Moreover, it examines whether these supports predict various aspects of observed teacher practice. These aspects include (1) process quality, or the extent to which teacher-child interactions are responsive and sensitive and classrooms are well-organized and well-managed; (2) instructional quality, or the extent to which teachers promote children's high-order thinking skills and provide rich language environments; and (3) the amount of time classes spend on language and literacy activities, on math activities, and in different activity groupings such as small group, whole group, and transitions. This report also explores whether the associations between professional development supports and teacher practice vary based on teachers' levels of experience. Data for this study come from Making Pre-K Count (MPC), a project that evaluated the effects of an evidence-based mathematics curriculum combined with teacher professional development on outcomes for 4-year-olds enrolled in center- and school-based pre-K programs in low-income neighborhoods in New York City. (author abstract)