For many high school student athletes, there is increased pressure to specialize in one sport, to participate at a high level, and to play year-round (Brenner, 2016). This increased emphasis on sport specialization has led to a proliferation of overuse injuries, overtraining, and burnout (Brenner, 2016). Sport specialization significantly contributes to overuse injuries, which account for almost half of all sport injuries (Andrews & Yaeger, 2013). This research was designed to clarify if there are significant differences in the behavioral and academic performance of student athletes who compete in one sport and student athletes who compete in multiple sports. Six high schools in southwest Missouri provided GPAs, hours absent, and days suspended for approximately 1,500 student athletes for the 2015-2016 school year. An ANOVA test was conducted to determine if significant differences existed among one-, two-, and three-or-more sport athletes for each individual area of study. When single-sport athletes were compared to multiple-sport athletes, significant differences were discovered in each area of study including GPAs, hours absent, and days suspended. In all instances of significant difference, multiple-sport athletes demonstrated improved academic and behavioral performance over single-sport athletes. These findings should assist students, coaches, parents, teachers, and administrators in decision-making about student athletics participation. [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.]