Study 1. Researchers at the University of Arkansas found that vouchers increase high school graduation rates.

University of Arkansas researcher Patrick Wolf led a team of evaluators who found that the offer to participate in the D.C. Opportunity Scholarship Program raised a student?s probability of completing high school by 12 percentage points, from 70 percent to 82 percent, based on parent reports. Some students declined to use their scholarships. Adjusting the data to account for scholarship decliners reveals that actually using a scholarship to attend a private school increased graduation rates by 21 percentage points.

Study 2. Mathematica Policy Research study concluded that KIPP (Knowledge is Power Program) charter school students outperform their counterparts in district schools.

By seventh grade, half of the KIPP schools studied showed growth in math scores equal to an additional 1.2 years of school. Reading gains for KIPP were not as dramatic but still significant, the researchers reported, reflecting an additional three-quarters of a year of growth.

Mathematica said it found no evidence that KIPP schools were systematically drawing students with more economic advantages from surrounding school systems. But attrition rates at the KIPP schools, measuring the portion of students who failed to complete four years at the schools, varied widely.

North Carolina has two KIPP charter schools.