Skeptics of KIPP argue that these schools rely on selective admission, attrition, and replacement of students to produce positive achievement results. However, data on student characteristics provide little evidence that KIPP “creams” or selectively enrolls higher performing students at the middle school level (Tuttle et al. 2013). The typical KIPP student scored at the 45th percentile within the district—that is, below the district average—in reading and math prior to entering KIPP. Nearly all KIPP students (96 percent) are either black or Hispanic, and more than four-fifths (83 percent) are from households with incomes low enough to make them eligible for free or reduced-price school meals—percentages that exceed the averages at the (non-KIPP) elementary schools they attended prior to enrolling in KIPP middle schools. In contrast, KIPP students are somewhat less likely than students at these feeder elementary schools to have received special education services (9 versus 13 percent) or to have been classified as having limited English proficiency (10 versus 15 percent) when they were in elementary school. Patterns of student attrition from KIPP middle schools are similar to those at nearby non-KIPP public schools (Nichols-Barrer et al. 2015). However, unlike traditional public schools in surrounding districts, when students exit, KIPP schools tend to replace them with higher-achieving students, and fewer students are replaced in the later years of middle school. Still, KIPP’s positive achievement impacts do not appear to be explained by advantages in the prior achievement of KIPP students, even when attrition and replacement patterns are taken into account (Nichols-Barrer et al. 2015).

That’s from the full report. These are the Key Findings:

• KIPP elementary schools have positive, statistically significant, and educationally meaningful impacts on three of four measures of reading and mathematics skills.
• Consistent with prior research, KIPP middle schools have positive, statistically significant, and educationally meaningful impacts on student achievement in math, reading, science, and social studies. Average impacts of middle schools were positive and statistically significant throughout the 10-year period covered by the study, though higher in earlier years than recent years.
• KIPP high schools have positive, statistically significant, and educationally meaningful impacts on student achievement for high school students new to the KIPP network. For students continuing to KIPP high schools from KIPP middle schools, impacts on achievement are not statistically significant. For this group of continuing KIPP students, KIPP high schools have positive impacts on a variety of college preparation activities and the likelihood of applying to college.
• On surveys of student motivation, engagement, behavior, and educational aspirations, KIPP schools showed no significant impact. However, KIPP elementary and middle schools had positive impacts on parent satisfaction.