The Knowledge Is Power Program (KIPP), a U.s. charter school network known for lifting the achievements of poor children through high standards and long hours of work, benefits from significant private funding and student attrition according to a new study from researchers at Western Michigan University. The study estimates that KIPP schools receive more than $5,000 a year per pupil through private donations in addition to regular sources of public funding. The study also found that about 15% of KIPP students leave the schools each year as they progress from sixth to eighth grades, and that those students often are not replaced.Gary Miron, the study’s author, said KIPP schools in Washington and elsewhere often outperform regular public schools, “but they’re not doing it with the same students, and they’re not doing it with the same dollars.”KIPP officials said that the study was riddled with errors because of flaws in the data that were analyzed. “The questions they ask are the right ones,” said KIPP spokesman Steve Mancini. “We reject their conclusions.”