The student teaching field experience has proven to be one of the most critical components of teacher preparation programs, and yet little is known about how pedagogical skills develop during this period. The purpose of this exploratory study was to examine student teachers' classroom interactions over the course of a 10-week student teaching experience to determine if interactions changed over time. Increases in student-centered interaction patterns could reflect the development of routines and automaticity that have been associated with expert teaching. Middle school student teachers (N=15) were observed for 6 weeks with the Brophy-Good Teacher-Child Dyadic Observation System. Frequencies of interactions were obtained, and patterns across three time periods were analyzed. Results of the study revealed significant differences across the three time periods: A U-shaped development pattern emerged for eight of nine variables: the interaction frequencies were lower in the middle of student teaching than during the beginning and ending periods. Possible explanations for the developmental pattern of the data are explored through discussion of three cognitive phenomena: cognitive restructuring, episodic growth, and paralysis of action. (Author/LL)