The results were more dismal for cyber charter schools: Students at 100 percent of them performed "significantly worse" than their counterparts in district schools.
The report does not identify the schools. Of the state's 135 charter schools, 74 are in the Philadelphia. The state also has 12 cyber charter schools.
"There is a wide disparity in Pennsylvania," said Devora Davis, research manager of Stanford's Center for Research on Education Outcomes (CREDO), which conducted the study. "It's a much different distribution than we've seen nationally."
CREDO examined Pennsylvania's charter schools as a follow-up to a 2009 report on charter school performance in 16 states. The researchers have not evaluated New Jersey's charter schools, but Davis said they had been talking to education officials about obtaining access to state data.
The Pennsylvania analysis showed that 30 percent of charter students performed significantly better than regular public school students in reading and 25 percent in math. Those results are far above the national average of 17 percent for high-performing charter schools.
But, on average, the state's charter school students lag behind the gains of students in regular public schools - 39 percent of charter schools underperform their public school counterparts in reading and 46 percent in math.
Nationally, students at 37 percent of charter schools perform significantly worse in both.
Thirty percent of Pennsylvania charter students performed about the same as traditional public school students in reading and 28 percent in math.
Nationally, about half of charter students do no better or worse than peers in district-operated schools.
Tim Eller, a spokesman for the state Department of Education, said officials had some concerns about the report, including that none of the charter schools was identified.
But he said the Corbett administration wanted to make sure charter schools were held to the same performance standards as district-run schools.
"I know that he is looking to work with the General Assembly to strengthen the charter school law to provide more accountability and oversight," Eller said.
"There was nothing in that report that was a surprise," said Robert Fayfich, interim executive director of the Pennsylvania Coalition of Public Charter Schools. "The issue is what we do to improve it."
He said the coalition, which represents most charter schools in the state, was trying to obtain information from CREDO to help it identify the top-performing schools so they could share their methods.
Coalition president Lawrence F. Jones Jr. said in a statement that his organization was working with charter schools across the state to figure out why some excel and others do not.
Jones, chief executive of the Richard Allen Preparatory Charter School in Philadelphia, added: "This is precisely why charters were created - not only to provide choice for parents, but to test alternative-education methods, learn quickly, and pass on what we learn from both our successes and failures."
The coalition has pledged to work with the legislature and state officials "to adopt uniform accountability and performance measures" to help improve all charter schools and "eliminate those schools that do not improve," he said.
The state's first charter schools opened in 1997 after the legislature passed the charter school law. Charter schools are taxpayer-funded and overseen by their own boards. They are exempt from some state regulations but must give students the state's standardized tests.
The CREDO study matched students in charter schools and district-operated schools by grade, race, income, and other factors. Their performance was then tracked using test results from 2006-07 through 2009-10.
Because the study required four years of data, researchers followed the performance of 73,085 students from only 116 charter schools and eight cyber charter schools, whose students receive online instruction in their homes. The study was limited to third through eighth graders because high school test scores were available for only 11th grade.
The entire report, "Charter School Performance in Pennsylvania," from Stanford University's Center for Research on Education Outcomes, is available at http://credo.stanford.edu/
Contact staff writer Martha Woodall at 215-854-2789 or email@example.com.