In West Virginia one arts credit is required for graduation. This study examined whether participation in arts instruction beyond the one-credit minimum correlated with improved academic proficiency. Method of study: We studied a cohort of 14,653 public high school students who stayed at grade level during the 4-year period from 2007 through 2010. Overall 37% of the students were economically disadvantaged and 11% were students with disabilities. Arts participation was defined as the total number of arts-related credits in all disciplines--music, visual arts, and performance arts--earned during students' tenure from Grade 9 through Grade 12. We used binary logistic regression to examine the presence and magnitude of associations between arts participation and proficiency (Mastery or above) in mathematics and reading/language arts on the WESTEST 2 and for scoring at or above the national average composite score on ACT PLAN. We also calculated the odds of achieving these outcomes relative to arts participation as a measure of effect size. Results of the study included the following: Findings: Students who earn 2 or more arts credits during high school were about 1.3 and 1.6 times more likely to score at proficient levels for mathematics and reading/language arts, respectively. Students who earned 2 or more arts credits also were about 1.5 times more likely to have scored at or above the national average composite score on the ACT PLAN. Significant associations between arts participation and reading/language arts proficiency held across subgroups of students with and without disabilities and/or economic disadvantage; however, for mathematics, we observed significant associations only for students with neither low family income nor disabilities, and students with low family income. The odds of scoring at proficient levels in reading/language arts among students with disabilities and students with both disabilities and low family income indicated that while few of these students reach proficiency they were up to twice as likely to do so if they exceeded the minimum number of arts credits required for graduation. Compared to earning a single arts credit, for mathematics there was no advantage in earning a second arts credit; however, students were about 1.3 times more likely to reach proficiency when earning 3 arts credits and 1.6 times more likely when earning 4 or more. The odds were better for reading/language arts. There was a slight advantage in proficiency for students earning 2 credits, but the advantage rose to 1.6 and 2.2 times when students earned 3, or 4 or more arts credits, respectively. While few students reached Above Mastery and Distinguished status, their odds of doing so increased somewhat if they earned additional arts credits. The odds of achieving Mastery in mathematics were only modestly improved--1.3 times greater when students earned 2 or more arts credits and 1.5 times greater for achieving Distinguished; but were slightly higher for reading/language, rising from about 1.4 times for Mastery to 2.0 times for Distinguished. Limitations of study: The highest grade WESTEST 2 is administered in is 11th grade, yet arts participation was measured through students' 12th-grade year. Likewise, the students completed ACT PLAN testing in 10th grade, 2 years prior to their scheduled graduation. Finally, the study was correlational and no claims were made as to causation.