This study examined the influence of field placements settings with varying demographic profiles on preservice elementary teachers. Data were gathered at three points during the participants' final year in their teacher preparation program in order to chart changes over time in science teaching self-efficacy beliefs. These measures were supplemented by interviews to investigate attitudes about teaching science in diverse settings. Gee's identity framework (2000) and the dimensions of teacher development described by Bullough et al. [Bullough et al. [2004] "Teachers and Teaching: Theory and Practice" 10:365-394] were employed as interpretive tools. Statistical analyses of teaching self-efficacy scores revealed marginal changes over time. Individual interviews revealed no discernible influence upon the teacher candidates' perceptions of science teaching selves that could be attributed to the demographics of their field placements. Emerging from this study was the previously underappreciated value of self-doubt as a factor in motivating preservice teachers. The findings call into question the tendency to use heightened teaching self-efficacy as an indicator of individual or programmatic success. This examination of preservice teacher development over the final year of a preparatory program, especially when considered in light of student diversity, demonstrates the soundness of Dewey's claim that uncertainty is a crucial component of learning and knowing. (Contains 2 tables, 2 figures, and 1 note.)