Thesis advisor: Michael Barnett / Scientific proficiency is important, not only for a solid, interdisciplinary educational foundation, but also for entry into and mobility within today's increasingly technological and globalized workplace, as well as for informed, democratic participation in society (National Academies Press, 2007b). Within the United States, low-income, ethnic minority students are disproportionately underperforming and underrepresented in science, as well as mathematics, engineering and other technology fields (Business-Higher Education Forum, 2011; National Assessment of Educational Progress, 2009). This is due, in part, to a lack of educational structures and strategies that can support low-income, ethnic minority students to become competent in science in equitable and empowering ways. In order to investigate such structures and strategies that may be beneficial for these students, a longitudinal, qualitative study was conducted. The 15 month study was an investigation of science identity negotiation informed by the theoretical perspectives of Brown's (2004) discursive science identities and Tan and Barton's (2008) identities-in-practice amongst ten high school students in an informal science program and employed an amalgam of research designs, including ethnography (Geertz, 1973), case study (Stake, 2000) and grounded theory (Glaser & Strauss, 1967). Findings indicated that the students made use of two strategies, discursive identity development and language use in science, in order to negotiate student science identities in satisfying ways within the limits of the TESJ practice. Additionally, 3 factors were identified as being supportive of successful student science identity negotiation in the informal practice, as well. These were (i) peer dynamics, (ii) significant social interactions, and (iii) student ownership in science. The students were also uncovered to be particularly open-minded to the field of STEM. Finally, with respect to STEM career development, specific behaviors were indicative of students' serious consideration of STEM careers and two major patterns in STEM career interests were uncovered. The findings are discussed in relation to existing research in science education, as are implications for future research and practice. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Lynch School of Education. / Discipline: Teacher Education, Special Education, Curriculum and Instruction.