Descriptive data were collected over a two-month period on two middle elementary classrooms to which student teachers had been assigned. From this data typical patterns of teaching/learning behavior were identified for each classroom. The student teachers were then interchanged, and the data collection continued for another two months. Comparison of data collected before and after the student teacher exchange revealed the persistence of some and the modification of other behavior patterns possibly attributable to the exchange. These results were used to generate hypotheses concerning possible relationships among selected components of the classroom ecosystem. (Author)