Nationally, public school districts utilize student achievement as the indicator of success or failure. In Texas, student achievement is measured by the yearly State of Texas Assessments of Academic Readiness (STAAR) assessment in Grades 3 through 12. Existing studies examined mentoring as a way of creating positive change for principals. Much of the literature is silent regarding the impact of principal mentoring on student achievement. Principal mentoring is the main component of the Texas Principal Evaluation and Support System (T-PESS). This led to the purpose of this quantitative casual comparative research which was to determine if mentoring public school principals is more likely to result in higher student achievement over students whose principals were not mentored. The research focused on determining the extent of differences in student achievement, determined by student performance on STAAR Reading in third grade in 2015 and 2017. Guided by the adult learning theories of Mezirow (1991) and Bolman and Deal (2017) and the mentoring theory of Kram (1985), this study utilizes archival academic data from the TEA and focused on approximately 130 elementary campuses located in a Texas suburban county. The data was analyzed and interpreted utilizing a paired samples t-test. The results showed that the 2015 passing mean was 89.09 while the 2017 passing mean was 85.1, with a p-value of 0.001, therefore the null is rejected, as there is a significant difference. It is recommended that further research be conducted on this topic utilizing multiple methods. [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.]