This study estimates the effects of open-enrollment charter schools on student performance in traditional public schools in Arkansas. The paper examines the change in Iowa Assessment scores for first and second graders across Arkansas school districts between the 2014-2015 and 2015-2016 school years. The ordinary least-squares regression estimates demonstrate a positive and statistically significant relationship between elementary charter school enrollment and traditional public school Iowa Assessment scores across districts, controlling for relevant factors. Improvements in traditional public schools' math, reading, and language test scores were greater in school districts that had a larger percentage of students enrolling in charter schools. The most influential impact of charter schools on predicted test scores was in math, where a 1% increase in elementary charter school enrollment led to a 0.13 predicted improvement in normal-curve-equivalent test scores across Arkansas school districts.