In a local middle school, students were not meeting standards on the state mathematics tests. The purpose of this qualitative study was to explore mathematics teachers' perspectives on effective mathematics instruction vis-a-vis the principles of the National Council of Teachers of Mathematics (NCTM). Within this framework, the 6 principles in the creation of quality mathematics programs included equity, curriculum, teaching, learning, assessment, and technology. Seven teachers from around the country participated; all met the criteria of a graduate degree in education, at least 5 years of experience teaching adolescent learners, and at least 3 years teaching mathematics. Participants were surveyed about their perspectives using a modified Delphi method. In Round 1, they listed practices that they believed were helpful in all NCTM content standards. In Round 2, they ranked all of the practices and provided rationales. In Round 3, they viewed Round 2 rankings/rationale and then rated the practices a last time. Qualitative content analysis was used to analyze Round 1; descriptive analysis was used to analyze ranking data from Rounds 2 and 3. The results revealed the most effective instructional practices for middle school mathematics in each of the NCTM content standards. With that information, a training plan was developed to give local mathematics teachers a tool with which to analyze their instructional practices and then integrate the effective ones based on the modified Delphi study results to improve their students' achievement. Implications for positive social change include providing the local site with a research-based teacher training plan to improve mathematics instruction and potentially 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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]