This action research project was aimed to improve geometry students' achievement and the retention in a suburban public high school over a one-year implementation cycle. The curricular design was influenced by Dweck's (2006) theories of growth mindset, educational standards, and directives outlined by the National Council of Teachers of Mathematics (2009) and Asante's (1987) theories of learning communities. Statistical findings indicated progressive improvements on the California Standards Test in geometry, though not significant; the percent of students who scored "proficient and above" remained relatively the same. Significant statistical findings indicated no third-quarter slump in grades, and ongoing improvement in the successive course. There were no significant gender differences in achievement, and ethnic differences could not be reliably tested because there were too few students of color. Retention data were confounded by a change in the academic counseling program where students who were earning Ds were urged to drop the course if they did not improve their grades. Survey findings showed that students identified several features of the curriculum that were strong: team-building activities; autobiographical stories of overcoming challenges; information from the "Learning and the Brain Online Program"; posting of vocabulary, postulates, and theorems; and reflections regarding preparations for assessments. They also noted some challenges: personalization of an intelligence growth article, the target age for the "Learning and the Brain Online Program", and a lack of time to understand and utilize all of the information. The geometry teachers, through journal entries and focus group discussions, identified numerous features of the new curriculum as being especially strong, including enhanced student efficacy, diminished stereotype threat, stronger relationships among students and between students and teachers, an enhanced sense of community, and stronger collegial relationships among the geometry teachers. They also noted two challenges: inadequate time to implement and discuss the lessons, and insufficient communication among the teachers regarding strategies and outcomes. Both groups offered recommendations for making curricular improvements as an ongoing action research effort. [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.]