This descriptive study by David Griffith examines how charter school enrollment within Metropolitan areas in the U.S. is related to student achievement overall, among economically disadvantaged students, and among students from underrepresented racial groups. Using data from the Common Core of Data and the Stanford Education Data Archive, the author compares achievement across grade levels that did and did not see an increase in charter school enrollment share within the same metropolitan area. The findings suggest that an increase in charter school enrollment is associated with higher math achievement for economically disadvantaged students and black students. When more Hispanic students are enrolled in charter schools in an area, they have higher math achievement scores. Metropolitan areas with higher charter school enrollment also have smaller math achievement gaps between white and black students and between economically advantaged and economically disadvantaged students. They do not find any achievement differences within English and Language Arts.