The No Child Left Behind Act of 2001 (NCLB) calls for 100 percent proficiency in reading and mathematics by 2014. The Act was supported overwhelming by both political parties and signified a major overhaul of the Elementary and Secondary Education Act of 1965. Using a questionnaire, this study examined teachers' perceptions regarding NCLB and the four variables: instructional practices, testing practices, professional development, and school climate. A total of 102 teacher questionnaires were distributed at a regularly scheduled faculty meeting. This study also examined teacher perceptions of NCLB, instructional practices, test preparation, professional development, and school climate within a high-stakes testing environment and a non-high-stakes testing environment. Further, this study examined the difference between teacher perceptions regarding the four variables, based on perceived school climate, in a high-stakes testing environment and non-high-stakes testing environment. The data yielded from this study was subjected to quantitative analysis. Mean scores and standard deviations were calculated for all the teacher responses for all variables in this study. Independent t tests were performed to analyze the results to determine if the mean values differed significantly on the four variables with respect to gender, tenure status, and high-stakes and non-high-stakes testing environments. Mean values were analyzed, produced significant results, and resulted in additional analyses of the items for each of the significant variables. A correlation analysis was calculated to determine relationships between and among all variables. School climate was the mediating variable and was included in the original analysis. The findings indicate that both teachers in high-stakes testing environments and teachers in non-high-stakes testing environments spend a significant amount of time on test preparation activities. Specifically, high-stakes teachers spend more time on test preparation activities. There may be environments in which test preparation is necessary for schools to be successful. The findings also indicate that professional development significantly affects the school climate of a building. Teachers who are more positive toward professional development are more likely to identify the school climate as focused on test preparation. [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.]