When the number of charter schools in a given area increases, are students who remain in traditional public schools worse off? This is a claim often made by opponents of school choice; gains made by students in charter schools, they say, come at the expense of students left behind. There is scant evidence to support this view in the existing literature, which suggests that charter schools have either no effect or even a small positive effect on students in traditional public schools. Admittedly, though, much of this research focuses on short-run test-score outcomes, and thus might miss any longer-term negative effects. Therefore, in this report, the author takes a more descriptive approach to the evidence on the relationship between charter schools and declines in public school quality. Using school-level test-score data across the United States made available by Stanford Education Data Archive (SEDA), the author shows that there is a very small but positive relationship between the proportion of students within a geographic district who attend a charter school as of 2009 and the test-score growth for students enrolled in the traditional public schools in the same district over the next seven years. The analysis in this report is intended not to show causality, but rather to show that the general pattern of test-score outcomes over this period is simply not consistent with the claim that charter school exposure for a meaningful period of time produces declines in the performance of traditional public schools.