"Our estimates imply that students in North Carolina do less well in charter schools than they would have done in traditional public schools and that the negative effects of attending a charter school are large," the study's authors wrote.DURHAM, N.C. -- State exam results indicate that most students at North Carolina's charter schools would perform better if they stayed in traditional public schools. The data is compiled in a new study co-authored by a Duke professor. It argues that, on average, students who attend charter schools are being academically harmed. "Our estimates imply that students in North Carolina do less...