K-12 education policy has recently received much scrutiny from policymakers, taxpayers, parents, and students. Reformers have often cited increases in spending with little noticeable gain in test scores, coupled with the fact that American students lag behind their foreign peers on standardized tests, as the policy problem. School choice, specifically charter school policy, has emerged as a remedy for these issues. School choice, by nature, has two hypothetical effects, participant and competitive effects. This discourse concentrates on the latter. I analyzed school level data from Ohio to determine if traditional public schools potentially threatened by competition from charter schools respond with positive test score gains. Ohio charter school policy changed in 2003, providing for a natural experiment via an exogenous shock to the system to answer this question. The threat of charter schools seems to have a small positive effect on traditional public school achievement levels.