Regarding School Voucher Programs:
Among voucher programs, random-assignment studies generally find modest improvements in reading or math scores, or both. Achievement gains are typically small in each year, but cumulative over time. Graduation rates have been studied less often, but the available evidence indicates a substantial positive impact. None of these studies has found a negative impact.
Other research questions regarding voucher program participants have included student safety, parent satisfaction, racial integration, services for students with disabilities, and outcomes related to civic participation and values. Results from these studies are consistently positive.
Among voucher programs, these studies consistently find that vouchers are associated with improved test scores in the affected public schools. The size of the effect in these studies varies from modest to large. No study has found a negative impact.Regarding Charter Schools:
Among charter schools, some high-quality studies show that charters have positive effects on academic outcomes. In other contexts, the findings are more mixed. In general, charters seem most likely to have positive effects on student achievement at the elementary level, in math, if the school is part of a well-established charter network such as the KIPP schools (Knowledge Is Power Program) if the student has been enrolled for a while, if the student is disadvantaged, and if the school is in an urban area.
Fewer studies have examined the competitive effects of charter schools on achievement in traditional public schools, and the studies that do exist vary greatly in quality. The more rigorous studies generally show that charter competition is associated with modest increases in achievement in nearby public schools. It seems clear that school choice poses no threat to academic outcomes in the public school system. Opponents predicted school choice would harm public schools, but that harm has not materialized.
A third area of study has been the fiscal impact of school choice. Even under conservative assumptions about such questions as state and local budget sensitivity to enrollment changes, the net impact of school choice on public finances is usually positive and has never been found to be negative.