The focus on measuring student growth based on teacher effectiveness has presented new challenges for an urban school in Massachusetts. The purpose of this general interpretive qualitative study was to examine the instructional practices of a group of middle school teachers, the practices they perceived to be effective for ensuring student success, and the methods teachers used to verify students' understanding of the learning content and objectives presented by the teachers. Vygotsky's social constructivism and Bandura's concept of self-efficacy provide the framework for understanding how teachers address the unique learning needs of students on a daily basis. The research question for the study examined teachers' perceptions of their own instructional effectiveness. Data were collected through interviews with 7 middle school teachers. The inductive and interpretive analysis method was used to analyze data and identify relationships within the data. Lesson plans and assessment tools were used for triangulation. Data revealed that teachers' level of confidence in their own teaching ability influenced their teaching approach and practice as well as the degree to which teachers diversified their instructional approaches to meet the needs of struggling students. In addition, teachers identified methods for checking student understanding and described their process of making daily adjustments to instructional practices in order to meet the needs of struggling students. Recommendations for improving instructional effectiveness include professional development aimed at equipping teachers to verify student understanding in daily instruction. This study is expected to contribute to positive social change by providing learning communities with empirically-based methods to improve 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.]