The purpose of this study was to examine if faculty trust in the principal mediates the impact of initiating structure and consideration on student achievement. Using social capital theory, the study focused on principals-teachers' relationships built on trust as a mediator of this impact since good schools tend to function well as a system of relationships. Social capital theory calls attention to the relationships existing among organizational members and the resources inherent in those relationships that can be tapped for desired goals. Because principals' leadership tends to influence student achievement generally through other variables, an indirect-effect model for principals' leadership was tested using a sample of teachers and students' test scores from Catholic schools in New York. Teachers' perceptions of principals' use of structure and consideration leadership behaviors as well as teachers' perceptions of principals' trustworthiness were analyzed to determine if and how the influence of such leadership behaviors on student achievement is by means of faculty trust in the principal. Controlling for school-level SES, analysis revealed a significant indirect effect of principals' leadership on student achievement through faculty trust in the principal, ab = 0.297, 95% BCI (0.002, 0.866) whose size, ab = 0.297 or approximately 0.3. Analysis thus confirmed faculty trust in the principal as an important school-level variable maximizing the relevance of principals' leadership for student achievement. Implications of findings for Catholic schools' leadership and student achievement are discussed. [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.]