Twenty-seven KIPP charter middle schools, including one in the District, have posted "large and significant gains" beyond what is average for urban schools, according to a report by the Educational Policy Institute.

The Virginia Beach-based research organization, using data provided by the Knowledge Is Power Program, said 1,800 mostly low-income black and Hispanic fifth-graders showed gains significantly above average in reading, language and mathematics from 2003 to 2004.

It was the largest study so far of KIPP, which has 48 schools in the United States, including three in the Washington area. Some experts have cited KIPP, begun by two teachers in 1994, as an example of what disadvantaged students can achieve if given more time in smaller schools, as well as firm homework requirements and well-trained principals with the power to hire and fire teachers.

Steve Mancini, spokesman for the San Francisco-based organization, applauded the results but said, "We won't be fully satisfied until our students finally earn acceptances to college."

Statistical experts said more data on KIPP and more independent assessments are needed before any conclusions can be reached on the organization's methods. Jeffrey R. Henig, a professor of political science and education at Columbia University's Teachers College, said some scholars have suggested that KIPP fifth-graders arrive with more motivated parents and other advantages compared with their neighborhood peers. More research on whether the gains are sustainable over time also is needed, Henig added.

KIPP officials said their data show incoming students to be just as disadvantaged as other children in their neighborhoods. Test results, they said, showed that new students starting fifth grade in 2004 at the KIPP school in Southeast Washington averaged 34.1 in reading on a 99-point scale called a normal curve equivalent, compared with 46.2 for their classmates in neighboring schools.

The Educational Policy Institute study used the same scale, which is different from percentile ranks most often used to measure achievement and criticized as confusing by some experts.

Students show no growth on the 99-point scale from one year to the next if they make normal progress. Fifth-graders at the 27 KIPP schools included in the study showed an average gain of 7.5 points in reading, 9.1 in language and 11.6 in mathematics from fall 2003 to fall 2004. Educational Policy Institute President Watson Scott Swail said he hoped next to compare KIPP students with students of very similar backgrounds who attend regular schools.

The KIPP DC:KEY Academy, the first KIPP school in the Washington area, opened in 2000 and has 320 students in grades 5 through 8. It has the highest math scores in the city, though more than 80 percent of its students come from black families poor enough to qualify for federal lunch subsidies. This summer, KIPP schools opened in the District and Annapolis, and KIPP officials said there are plans for a third middle school and a high school in the District.

KIPP students are in school at least nine hours a day, compared with fewer than seven hours in regular public schools. Three weeks of summer school is mandatory. Students are urged to call teachers at home if they have questions about homework. Those who do not complete homework are disciplined. Good work and behavior are rewarded with points toward items from the student store and school trips, from which students with few points are excluded. Teachers are trained to be very active in their classrooms, involving all children in lessons and taking points off from those who do not pay attention.

Mike Feinberg and Dave Levin started the first KIPP fifth-grade program at a Houston elementary school. The 50 students' passing rate on a state test doubled in the first year.