The purpose of this study is to understand how teacher identity influences elementary teachers' science practices from multiple perspective---the teacher's self-reported identity, the researcher's perspective, and the students' perspectives. Two frameworks on identity were synthesized and used in this research. The first, developed by Gee (2000-01) examines "who a teacher is" with respect to four areas: nature, institution, discourse, and affinity group belonging. The second, developed by Beijaard, Verloop, and Vermunt (2000) examines factors that drive what a teacher does in his/her practice through examining teachers' expertise divided among three areas: content, pedagogy, and didactics. These frameworks were used to guide interpretation of the data sources in order to better understand how instruction unfolded. The science instruction of one class of second grade students receiving science instruction from three different teachers was studied over the course of one school year. The first manuscript of this study is a qualitative case study describing the three teachers' identities and practices from the perspective of the teacher, researcher, and students. Classroom observations, teacher interviews and questionnaires, and student interviews were coded thematically using identity markers as themes. These data sources were triangulated to reveal differences in both the identities and practices among the three teachers. For two of the three teachers, their self-described identities were different from how they were viewed by their students and the researcher. These findings highlight the importance of incorporating multiple perspectives, including those of students, when describing teachers' practices and identities. The study revealed that the three experienced teachers at the same grade level had vastly different science needs, underscoring the utility of identity theory for the design of professional development efforts. The second manuscript of this study is a mixed-methods analysis of the science notebook entries created by each of the students in this second grade class over the course of the school year. Every entry of every notebook was photographed and coded for: unit (and therefore teacher), inquiry phase (pre-, during-, or post-investigation), and driving force (teacher-driven, student-driven, or balanced). In addition, missing and incomplete notebook entries were also documented. Quantitative analysis looked at the frequency of entries based on these codes. Qualitative data included thematic descriptions of how each teacher used the notebooks, teacher interviews, student interviews of their notebook use and classroom observations. All three teachers used similar curricular materials (kits) and received training from the school district on using science notebooks, suggesting that they would likely use the science notebooks in a similar way. However, quantitative differences were found across all three areas (inquiry phases, driving force, and missing entries), and qualitative analysis also indicated each teacher used the notebooks in a very different way. The teacher identity framework provided a useful way of interpreting these differences. These findings suggest that student science notebook analysis can be used in concert with other data sources through an identity framework to provide information about instruction over the course of a unit or school year, providing more robust analysis than classroom observations and interviews alone. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]