Association for Public Policy Analysis & Management

Charter school enrollment has grown rapidly in the U.S. in recent years, increasing from under 500,000 students in 2000 to about 3 million students today (NCES 2017). Market share is particularly high in several cities—including New Orleans, Detroit, Washington DC, and Philadelphia—where charter schools enroll over a third of public school students.

KIPP is a charter network that has grown rapidly, and now includes over 200 elementary, middle, and high schools serving 90,000 students. Prior studies have found that KIPP schools positively affect student achievement (Tuttle et al. 2015, Gleason et al. 2014). There is less evidence on how KIPP impacts have changed over time, but Tuttle et al. (2015) found that they were largest in 2007 and earlier, especially in math, ranging from 0.38 to 0.50 standard deviations. In 2014, math impacts remained positive but were smaller (0.24).

These patterns of declining KIPP impacts raise a number of questions. Although we know that the average network-wide impacts declined over this period, the network also grew rapidly over this period. Did the impacts of the early, successful KIPP schools decline over this period? Or were network-wide impacts pulled down by less effective schools joining the network more recently? Nor do we have information on what factors might be related to the lower impacts in more recent years. While the overall KIPP network grew over this period, there is variation across districts: in some cities the number of KIPP schools grew more rapidly than in others. There was also variation in whether and when the network—which originally included only middle schools—expanded to the elementary and high school levels. It could be that the impacts of KIPP middle schools began to decline when the network expanded to include these additional levels.

Understanding the trends in the effects of a successful and expanding charter school network may shed light on whether urban charter schools more generally, which have been found to have positive impacts for their students, may be a promising strategy for serving larger numbers of disadvantaged students. In this paper, we examined the impacts of KIPP middle schools between 2005 and 2014, when the number of KIPP schools increased from 40 to 140, to investigate which factors may have contributed to the decline in average impacts over this period. We found:

• The decline in the network-wide average impact of KIPP schools was driven largely by a declining time trend for individual schools over this period rather than by changes in the composition of KIPP schools in the network.
• There was a U-shaped relationship between the year the KIPP school opened and its impacts. KIPP schools that opened earliest and most recently had the most positive impacts on student achievement.
• Individual KIPP schools were least effective in their initial years of operation.
• The impacts of individual KIPP schools were not affected by the number of KIPP schools operating in the same city.