OFFICIALS OF KIPP (Knowledge Is Power Program) have become accustomed to the doubters who think the success of the fast-growing charter-school network is too good to be true. KIPP’s positive outcomes are the result not of its unique learning approach but rather, so the familiar critique goes, of its ability to attract the best students with highly motivated parents. Now comes rigorous research that should put an end to those suspicions and hopefully prompt discussion of what other schools might take away from KIPP’s experience in working with low-income students.

A study conducted by the independent firm Mathematica Policy Research, which analyzed data from 43 KIPP middle schools, found that students in these charter schools showed significantly greater learning gains in math, reading, science and social studies than did their peers in traditional public schools. The cumulative effects three to four years after entering KIPP translated, researchers found, into middle-schoolers gaining 11 months of additional learning growth in math and social studies, eight months in reading and 14 months in science. KIPP, which operates in 20 states and the District, is portrayed as among the highest-performing school networks in the country.

Debunking claims that KIPP’s success is rooted in “creaming” the best students, researchers found that students entering KIPP schools are very similar to other students in their neighborhoods: low-achieving, low-income and nonwhite. A typical student enrolling in a KIPP school scored at the 45th percentile in his or her school district in reading and math, lower than both the average in the school they attended and the school district as a whole.

As to whether KIPP finds ways to shed its low-performing students, the study determined that 37 percent of KIPP students depart through attrition, in line with school district attrition rates. To further address the issue, the study held KIPP accountable for the achievement of students who transfer out, even in the years after they depart KIPP schools. The study compared parents of children who won lotteries for a KIPP slot with those who were unsuccessful and found no difference in the amount of encouragement or support children receive after students had spent time at KIPP.

What is different is a high-intensity approach to learning in which KIPP students are in school longer (an average of 9 hours a day, for 192 days a year, compared with 6.6 hours per day, for 180 days, for traditional schools) and spend an additional 35 to 53 minutes on homework each night. Whether these methods can be adopted by traditional public schools is unclear; even KIPP officials acknowledge the difficulty of successfully ramping up operations. But it should be equally difficult to turn a blind eye to this study and not consider the possibilities its findings offer other children.