This is the first national study of the productivity of public charter schools relative to district schools. This report is a follow up to the charter school revenue study, "Charter School Funding: Inequity Expands" (see ED581409) in April 2014 by the School Choice Demonstration Project at the University of Arkansas. While the revenue study sought to determine whether there was a funding disparity between charter and traditional public schools (TPS) students, and if the gap has been closing or growing over the past nine years, this report extends the scope of that research by asking a different but related question: What is the relative productivity of public charter schools and TPS, both in terms of their cost effectiveness and their return on investment (ROI)? If funding is equal across the two sectors in a given state, the school sector that generates larger student achievement gains is more productive. If student achievement gains are equal across the two sectors in a given state, the school sector that receives less per pupil revenue is more productive. The authors explore these issues in this analysis of charter schools and TPS across 28 states and the District of Columbia. They use a cost effectiveness analysis as their first measure of productivity to consider how many test score points students gain on the 2010-11 National Assessment of Educational Progress (NAEP) for each $1000 invested in their public education in the charter compared to the TPS sectors. Secondly, they measure productivity by calculating a return on investment (ROI) by converting the learning gains developed over time by students in the public charter and TPS sectors into an estimate of the economic returns over a lifetime for students and comparing those returns to the revenue amounts invested in their education. The findings indicate that charter schools are more productive than TPS, either because they produce higher student gains at a lower cost or because they produce similar or only slightly lower student outcomes at a significantly lower cost.