Thirty-two percent of students in the Philadelphia School District attend charter schools, and the city ranks eighth in the country in the percentage of charter students, according to the National Alliance for Public Charter Schools.

That's a decrease from 2014-15, when 33 percent of the district students were in charters and Philadelphia was seventh nationwide. The changes reflect the closing of a few city charters. Charter enrollment in the city slipped from 64,090 in 2014-15 to 63,520 in the last academic year, while enrollment in district schools grew from 130,660 to 132,180 in that period.

And in a report on charter enrollment being released Thursday the alliance said growth in the number of students attending charter schools in Camden between 2014-15 and 2015-16 had boosted that city's percentage from 28 percent to 34 percent and pushed Camden into the seventh spot nationwide.

It marks the first time that Camden was listed among districts with the largest shares of charter enrollment, the alliance said.

The report is the 11th the charter-advocacy organization has released since it began tracking yearly enrollment. It found that nearly 2.9 million students - more than 6 percent of students nationwide - attended charter schools in 2015-16.

Nearly all the 17 districts with the largest charter enrollments are in urban centers. In three of them, charters enroll more than half the students. New Orleans, where 92 percent of students attend charters, was followed by Detroit and Flint, Mich., where 53 percent of students in both cities are in charters.

For the first time, the National Alliance included information in its new report about students' academic performance. In districts where charters had at least 30 percent of the students, the report said, in most cases charter students performed better on state tests in 2015-16 than their counterparts at traditional public schools.

In Philadelphia, where charter students made up 34 percent of the students tested, they represented 38 percent of those who scored proficient.

The difference in Camden was more pronounced. Charter students were only 31 percent of students tested in Camden; they accounted for 69 percent of those who scored proficient, the report said.

"We're pleased to see evidence that as the charter movement is growing, these schools are having a real impact in their districts," Nina Rees, president and CEO of the National Alliance, said in a statement. "Seeing that, nearly across the board, charter schools helping more students become academically proficient than their district counterparts helps explain the overwhelming parent demand we're seeing for charter schools."

The report is at odds with other recent studies that found that academic performance at charters was uneven.