An organization that represents more than three dozen D.C. charter schools filed a federal lawsuit against the District on Wednesday, alleging that the city has failed to provide uniform operating funds for charter and traditional schools as the law requires.

The D.C. Association of Chartered Public Schools argues that the city has spent about $2,150 less per charter student each year since 2008 than it has for students in the D.C. public school system.

In all, the city has given charter schools an estimated $770 million less than it should have since fiscal 2008, according to the complaint filed in U.S. District Court. The association and two other plaintiffs, Eagle Academy and Washington Latin public charter schools, say they turned to the courts as a last resort.

“We have not wanted to sue. We have wanted to work this out through other means, but it has not been possible,” said Ramona Edelin, the association’s executive director. “We just want the law settled. The law says that charter school students should receive equal and uniform funding to those in DCPS, and they do not.”

Spokesmen for Mayor Vincent C. Gray (D) and Chief Financial Officer Jeffrey S. DeWitt, who were both named as defendants, referred questions to Attorney General Irvin B. Nathan.

Ted Gest, a spokesman for Nathan, said city lawyers reviewed the complaint and believe it is “without merit.” Nathan previously addressed charter advocates’ concerns in 2012, opining in a letter that the city’s additional spending on the traditional school system is legal.

Read the D.C. charter lawsuit

The complaint

An organization that represents more than three dozen D.C. charter schools filed a federal lawsuit against the District on Wednesday, alleging that the city has failed to provide uniform operating funds for charter and traditional schools as the law requires. Read the lawsuit.

The lawsuit follows years of school-funding debates that have pitted charter advocates against government officials and traditional-school advocates, who have maintained that traditional schools always will be more expensive to operate because of their mandate to serve all students and their role as community centers.

Both types of schools receive approximately $9,000 to $50,000 per student, depending on grade level and the level of need for special services. But millions of additional taxpayer dollars flow to the traditional school system outside those per-pupil payments, according to charter advocates and an independent commission’s report to the D.C. Council in 2012 and a government-commissioned study on school funding released in January.

“These disparities are contrary to D.C. law” and “have become a significant source of tension between the two sectors,” said the report, known as the D.C. Education Adequacy Study.

Charter school advocates who had long considered filing a lawsuit over inequitable funding were heartened by the study’s direct acknowledgment of their situation, Edelin said. They decided to hold off on filing the lawsuit, hoping that Gray would address the problems in his fiscal 2015 budget proposal, released in the spring.

Although the spending plan did take some steps toward equity, charter advocates said they were upset that Gray — who was elected in 2010 after promising funding parity for charters — didn’t go further.

“We feel like we’ve tried everything possible to get a solution to this politically,” said Robert Cane, executive director of FOCUS, a pro-charter group that helped recruit plaintiffs for the case. “I really believe they know they’re not doing the right thing, but they haven’t been able to stand up and do what’s right.”

Congress opened the door for charters in the nation’s capital when it passed the D.C. School Reform Act of 1995. The act required the city to set up a “uniform formula” to fund charter and traditional schools equally on the basis of enrollment.

Charter leaders say that the city’s funding structure has passed more money to traditional schools and has shortchanged the 44 percent of city students who are enrolled in charters, including by making it difficult for schools to pay competitive teacher salaries.

The lawsuit is the latest sign that despite recent efforts to improve cooperation between traditional and charter schools in the District, there are many unanswered questions about how the two sectors — which compete for students and resources, and which operate under different sets of expectations and constraints — should coexist.

The complaint filed Wednesday lays out several ways in which traditional schools receive taxpayer support that isn’t available to charter schools, echoing the arguments that charter advocates have presented in years of D.C. Council testimony and newspaper op-eds.

Much of the extra resources come in the form of in-kind services from other city agencies, such as facilities maintenance by the Department of General Services or legal representation by the Office of the Attorney General. D.C. Public Schools received about $66 million in such in-kind support during the 2014-2015 school year compared with $5 million for charters, according to the adequacy study.

DCPS is paid on the basis of its projected enrollment; when the school system overestimates its population, as has often been the case, it does not have to return the money it received for students who never came to class. The city also has provided supplemental appropriations to help cover DCPS cost overruns and has covered the school system’s debts and pension payments directly.

Charter schools are financed with quarterly payments based on the number of students actually enrolled during the city’s official student census each October.

Abigail Smith, the deputy mayor for education, has previously said that while the city can and should shrink its subsidies for traditional schools, those subsidies might never go away completely because of fundamental differ­ences between the two sectors.

The traditional school system must maintain enough space and staff across the city to serve any student who shows up throughout the year, for example, while charter schools don’t have that same obligation. Although DCPS may fall short of its enrollment projection in the October census, it sees a net influx of students throughout the year, schools officials have argued; charter schools see a net outflow, according to a 2013 city study, but they are allowed to keep the per-pupil payments even for those students who withdraw.

Some city leaders and advocates for traditional schools argue that it doesn’t make sense to fund both sectors equally when charters, by definition, are free from many of the rules that apply to DCPS, including the requirement to use union labor.

But the plaintiffs say that those are policy arguments that ignore the black-and-white requirements of the law. Their complaint ­hinges in part on the city’s unique legal status as a federal district subject to congressional oversight: They argue that the local government doesn’t have the power to pass laws and implement policies that contradict the equal-funding mandate in the School Reform Act.

The District’s lack of self-determination is a sore spot for city leaders who have chafed at what they see as Congress’s meddling in local affairs. The issue has been laid out publicly with the effort of Rep. Andy Harris (R-Md.) to roll back a city law decriminalizing marijuana.“We’re not anti-home rule,” said Cane, of the pro-charter group FOCUS. “We all live in the District and we all get home rule, but what we have here is a problem of fairness. The District is operating in an unfair way.”