A non-experimental research study was performed in which the researcher investigated the relationship between principals' use of transformational leadership practices and students' reading and mathematics achievement. A sample of principals from 2,500 randomly selected elementary, middle, and high schools in New York State were recruited by e-mail. Each principal was invited to respond to a survey administered via the internet using Qualtrix software. The survey was designed to assess the extent to which the principal uses transformational leadership practices. Transformational leadership style was measured by the Multifactor Leadership Questionnaire (MLQ), developed by Avolio and Bass (2004). The MLQ is a self-report instrument consisting of 45 Likert scale rating items that yield scores on three leadership domains: transformational, transactional, and passive avoidance. Student achievement was measured by mean student scores for each school on the 4th and 8th grade levels. New York State high school Regents assessments were used for reading or English Language Arts (ELA) and mathematics. An ANOVA and MANOVA analysis were used to assess the magnitude of relationship between leadership style practice scores and mean student scores on New York State reading and mathematics assessments. In addition, a Chi-Square test for independence analysis was conducted to determine if significant differences were found between leadership style and institutional level. A secondary analysis was also performed that included a Chi-Square test of independence to determine significant differences between gender and leadership styles. It was hypothesized that there will be no significant differences in leadership styles and reading and mathematics achievement. The findings of this analysis refuted this hypothesis. In addition, findings for the hypothesis to determine significant differences in leadership style and level of institution were supported because no differences were found to be significant. [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.]