Charter Schools represent a small share of the national education market: just 6.2 percent of all public schools and 4.6 percent of all students. But their rapid growth over the past two decades has captured an outsized measure of public attention, especially in communities where district and charter schools operate side by side. At New York City's Success Academy, a network of 46 schools, leaders are in a near constant battle with city education officials for the space in under-utilized public-school buildings that will allow their programs to continue to grow, despite long waiting lists and well-documented academic gains for Success students. These pitched battles often follow a similar script about the potential "spillover effects" of public charter schools on non-charter students, one which has informed political campaigns, protests, and even lawsuits. To shed light on the question of spillover effects, the author used data from New York City to estimate the effects of charter schools on students in two types of nearby district schools: those in the same neighborhood, and those that are co-located (in the same building). The findings show that communities can expand charter schools to meet growing demand without putting district schools at risk of instability or failure. Far from an existential threat to their district-school neighbors, public charter schools can benefit not only their own students but also those in other programs down the street--or hallway.