The No Child Left Behind Act of 2001 (NCLB) has had significant and multilayered consequences for students, teachers, and schools. The purpose of this study was to learn more about the areas of NCLB that teachers support and also the areas of NCLB that teachers see as problematic. The data in this mixed methods study was collected through an anonymous online survey. The survey asked teachers about the effects of NCLB on their schools, classrooms, and teaching practices. The 251 third through eighth grade teachers of reading/language arts, and/or math in this study work in a single culturally and economically diverse, elementary school district in the southwestern United States. I compared the perspectives of teachers within subgroups, including their schools' adequate yearly progress (AYP), and years of experience. NCLB is based on the theory of action that if sanctions are imposed on schools that do not make AYP, the teachers will change their practice to increase student scores on state mandated tests. The majority of all teachers in this study responded that they felt pressure to increase student test scores, which suggests that NCLB has changed teachers' practices. Overall, teachers in schools that missed AYP at least once over the previous four years and teachers that were new to the teaching profession were more positive about the effects of NCLB than teachers in schools that always made AYP or veteran teachers. There were also differences in the areas of NCLB that teachers viewed as positive or negative. Teachers with the most positive perspectives of NCLB tended to agree the most strongly with questions assessing the effects of NCLB on improving classroom instruction. Teachers with the most negative views of NCLB tended to view the broader effects of NCLB on teachers, schools, and education the most critically. Key themes in the qualitative data included the effects of NCLB on special populations of students, and on teachers and schools, and teachers' perceptions of the lack of parent and student accountability for student achievement. While most of the comments were negative, some teachers acknowledged that teachers should be held accountable for student achievement. [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.]