We estimate the spillover impacts of charter schools on public schools and public school students. We leverage administrative data and quasi-random assignment of charter school openings in Texas using application scores from the State Board of Education. This design capitalizes on the discontinuous increase in approval likelihood for charter school applications that score above a specific threshold to eliminate bias from charter schools' strategic location choice. Preliminary results suggest positive and sizable spillovers on public school test scores and that competition changes public schools' sociodemographic composition. Future work will analyze the mechanisms, including the within-school allocation of instructional resources, as well as student-level impacts on longer-term outcomes.