(CBS) — A new report claims to show that Chicago charter schools are lagging behind their traditional public counterparts, reports WBBM’s Nancy Harty.

The study from the University of Minnesota Law School says charter students trail conventional Chicago Public School students in math and reading by about two percent. The biggest difference is in graduation rates.

Author Myron Orfield says traditional public schools have a 13 percent higher rate and the comparison isn’t a flattering one.

“Chicago Public Schools have some of the lowest scores in the country on these kinds of issues,” Orfield said. “It is not a question Chicago Public Schools are doing great it’s just the charters are worse.”

Andrew Broy, president of the Illinois Network of Charter Schools, says the study is completely wrong about graduation rates because he says they are higher in charters.

“I don’t think this report contributes meaningfully to the charter discussion,” Broy said. “I think there have been studies done in the previous couple of years that are far more sophisticated.”