This study examined the effects of extracurricular absences on final grades and State of Texas Assessment of Academic Readiness (STAAR) End-of-Course (EOC) scores. A multiple regression test was run to determine whether there was a significant relationship between the grades of students with extracurricular absences and their STAAR EOC scores. Participants were freshmen who participated in extracurricular activities while enrolled in STAAR English 1 and/or Biology. The setting was a 4A high school in a suburb of a major city in central Texas. The school competes yearly for the Texas Cup, finishing in the top 10 in 9 of the past 10 years. The dependent variables in the research were participation in extracurricular activities, grades (in numerical form), and scores on the STAAR EOC tests. The independent variable was the number of absences due to participation in extracurricular activities. The results of the regression model showed significance that students with extracurricular absences scored higher on STAAR EOC tests. The regression also showed other factors, such as how a student performs on other STAAR EOC tests, to be a predictor of how a student will perform on STAAR EOC tests. English 1 STAAR EOC scores had the most significant effect on EOC test scores. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]