In 2015-16, the United States spent over $660 billion on its public education system in hopes of providing children with greater opportunities to excel academically and to improve their life trajectories. While public education dollars have risen at a relatively fast pace historically, future challenges, including underfunded pension liabilities, suggest policymakers should economize wherever possible. Meanwhile, the number of public charter schools has increased exponentially. From 1991 to 2018, charter school legislation passed in 44 states and the nation's capital, and student enrollment in charters increased to around 3.2 million. Since educational resources are limited, the authors examine which types of schooling offer society the biggest "bang for the buck." Both cost-effectiveness and return-on-investment (ROI) analyses compare the productivity of different organizations providing a similar service -- in this case, public education. The authors examine the differences in cost-effectiveness and ROI for public charter schools and traditional public schools (TPS) in eight major U.S. cities: Atlanta, Boston, Denver, Houston, Indianapolis, New York City, San Antonio, and the District of Columbia. Overall, they find that public charter schools outperform TPS on both productivity metrics overall and for all eight cities. They conclude that public charter schools in these eight U.S. cities are a good public investment in terms of the comparative amount of student achievement they produce for the funding they receive.