On average, charter schools perform at about the same level as traditional public schools. But an overall estimate disguises considerable variation in charter school impacts. Urban charter schools and those serving low-income and minority students, a number of which share a no excuses philosophy, tend to produce the largest gains. Expanding these highly effective charters and their practices may be a way to close achievement gaps. Research shows that charters can expand successfully and that traditional public schools that adopt charter practices (or are taken over by charter operators) can also make large academic gains. But to have a meaningful impact on nationwide achievement gaps, charter school approaches would need to be adopted beyond the charter sector itself. Any interventions that are built around using charter schools to close achievement gaps should focus not on the type of school but on the practices that work in the most effective charter schools.