Predictive studies of non-cognitive personality traits and SAT on college GPA are well established, but far less is known about the association between personality traits and comparable secondary school admission tests on secondary school GPA. This study assessed the relationship between the personality domains in the HEXACO: Personality Inventory-Revised (HEXACO: PI-R) inventory and secondary school GPA, while controlling for performance on the Secondary School Admission Test (SSAT). The results of the hierarchical regression analysis demonstrated no association between the HEXACO domains and GPA and a significant association between SSAT and GPA. The use of the personality domains in the HEXACO: PI-R inventory does not significantly add to prediction of high school GPA, while the SSAT is a strong predictor of academic success in a secondary school population, accounting for approximately 31% of the variance. [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.]