This three-year ethnographic study analyzes the ways in which "toxic" school culture was produced through interactions among staff members at Centerville High School, an under-resourced high school where I conducted fieldwork from 2004-2007. Using discourse analysis, I examine adults' competing beliefs about low-income and minority students, and I analyze the ways in which differences in belief immobilized the staff in a larger school reform effort. Against this backdrop, I trace the attempts of one small group of teacher-leaders to change their own discourse interactions as they grappled with difficult questions about race and class in their work toward school change. Fieldwork consisted of visits to the school three times each week during the first two years of the study followed by daily visits during the third year, resulting in over 1000 hours of participant observation and over 4000 pages of fieldnotes. Intensive fieldwork was coupled with extensive audiotaped ethnographic interviewing of more than 50 staff members during the third year in order to analyze individuals' sense-making processes within the larger school culture. Through a series of ethnographic vignettes embedded in a narrative account of the school reform effort, I illustrate the ways in which adults' race- and class-based belief systems gave rise to behaviors that unwittingly sustained toxic culture. I argue that the widespread helplessness and frustration which plagued Centerville staff members developed in large part because adults were unwilling to talk publicly about the dilemmas that shaped their work with low-income and minority students. Adults who were unable to meet the instructional needs of these students developed "place-specific expectations" which they used to justify lowered academic standards, and they positioned students as destined for low achievement "because" of their race and class status. Students responded by engaging in patterned interactions with staff members that contributed to a self-fulfilling prophecy of academic failure. Racial tension in the school further complicated interactions between adults and students and further precluded talk across ideological differences. Although discourse clashes created toxicity in Centerville, I argue that close examination of discourse can allow staff members to see the sources of their assumptions and beliefs about students, and in turn, develop new understandings about the complexities of teaching and collaborating across race and class differences. Furthermore, individual stories of growth and change reveal that when staff members admitted what they did not know about teaching low-income and minority students, they opened up a productive and necessary space for grappling with the challenges of work in urban and under-resourced settings. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]