In an economically disadvantaged part of Charlotte, N.C., there is a public school with the highest percentage of Title 1 students in the district. Less than a mile away is a charter school that could have become its competition, luring away students and leaving the district school with fewer funds to tackle the same set of challenges. Across the country, that’s how district and charter relationships often play out. They are competitive, rather than collaborative. But that’s not what happened in Charlotte.