Atlanta charter schools won a victory to preserve their public education funding Monday when the Georgia Supreme Court unanimously ruled that the city’s school system can’t make charters share in the burden of paying off a giant pension debt.

The state’s highest court decided that the amount of money charter schools receive is set by state law, and Atlanta Public Schools can’t reduce their funding to pay for system-wide expenses like the pension liability.

The decision leaves Atlanta’s traditional public schools having to pay off an old pension liability that has ballooned to about $550 million.

It also sustains the city’s charter public schools, which argued that their growth could be stunted if they had less money to work with.

“APS’ decision to withhold funding from start-up charter schools in order to pay for the district’s decades-old unfunded pension obligation was a violation of state law. This ruling is the final step int he judicial process related to this issue — there can be no further appeal,” wrote Matt Underwood, executive director for Atlanta Neighborhood Charter School, in a letter to families Monday.

The decision means that $415,000 will be released to Atlanta Neighborhood Charter School after the money had been withheld last school year for a pension payment, Underwood said.

The charter schools argued to the Georgia Supreme Court in June that they shouldn’t be responsible for a pension debt that they have nothing to do with. The debt has been accumulating since the late 1970s, and charter schools don’t participate in Atlanta Public Schools’ pension system.

But Atlanta’s public school system has said that all schools in the district share services, and charter schools shouldn’t be exempt from having to deal with the school district’s financial problems.

“While local boards of education have authority to manage and control the school system within their territory … they must do so in compliance with applicable constitutional and statutory laws,” according to the Georgia Supreme Court’s decision, written by Chief Justice Hugh Thompson.