A new report finds that the per-student funding gap between D.C. public schools and charter schools stood at $13,000 in 2011, the biggest gap in five cities that were studied.

The report commissioned by the Walton Family Foundation—yes, the Waltons of Walmart fame, who broadly support charter schools—found that from 2007 to 2011 per-student funding for D.C. public schools grew to $29,145, while over the same time period it only jumped to $16,361 for charter schools.

The disparity was larger than those in Newark, Los Angeles, Milwaukee, and Denver, though over the time period funding for D.C. charter schools grew at a faster clip than it did for public schools, 8.6 percent to three percent.

In theory, all schools in D.C.—public and charter—should get the same amount of money per student, $9,124 for the current fiscal year and $9,306 for the upcoming one. D.C. public schools, though, benefit from not having to pay for facilities and can take advantage of their size to negotiate more favorable contracts. D.C. charter schools have long complained that they’ve had to fight for space on the open market, using the $3,000 per-student facilities funds they get from D.C.

Enrollment in charter schools has grown much faster than it has for public school in recent years; in the 2011-2012 school year, charter school enrollment jumped 10 percent, while public school enrollment only increased by one percent. All told, 43 percent of the city’s public school students now attend a charter school.

The Waltons have been giving big money to promote D.C. school reform for years; in 2010, it amounted to $157 million, including money for teacher raises as part of a new contract. Last year their foundation commissioned a study on the quality of schools throughout the city, a study that advocated closing a number of low-performing public schools.