OAKLAND — Two Bay Area school districts lost a total of $76.6 million to public charter schools during the 2016-17 school year, a new report concludes.

The Oakland Unified School District lost $57.3 million and San Jose’s East Side Union High School District $19.3 million, according to the report.

Published Tuesday by think tank In The Public Interest, the report compared the school districts’ 2016-17 budgets to what they could have been if 15,487 students in Oakland’s charters and 4,811 in East Side Union’s charters enrolled in traditional public schools instead. The state allocates money to school districts based on their daily student attendance figures.

After factoring in how much the school districts potentially save by educating fewer students, the report’s authors determined the net fiscal impact of charter schools on the two districts. The report also found that the San Diego Unified School District lost $65.9 million to charter schools last school year.

The California Charter School Association issued a statement Tuesday condemning the report, saying it “does more harm than good for public school families and educators” by “unfairly scapegoating” charter schools.

“Charter public schools are an essential partner in a school district’s mission to provide all students with a high-quality public education and are a valuable part of California’s public education system. But they are not responsible, nor do they have control over, any district’s financial decisions,” the statement read.

University of Oregon Labor Education and Research Center professor Gordon Lafer, who led the yearlong study, told this news organization that the purpose of “Breaking Point: The Cost of Charter Schools for Public School Districts” was not to advocate for or against charter schools but rather to provide a first-of-its-kind analysis of how they impact school districts’ financial health.

The report also proposes changing California’s charter authorization law. Under the current law, school district, county and state officials cannot take potential financial impacts on existing district schools into account when authorizing charters. Lafer said such analysis should be required.

“The point of the study is that we can’t pretend this cost is zero,” Lafer said.

Efforts by legislators to change the law are underway. Senate Bill 1362, introduced in February by Sen. Jim Beall, D-San Jose, would allow governing boards to deny charter school petitions based on their effects on the rest of the district.

East Side Union High School District Superintendent Chris Funk has been outspoken for SB 1362, which is parked in the Senate Education Committee. He also supports Lafer’s recommendations.

“There needs to be more flexibility in the law when a school district can demonstrate declining enrollment or the concentration of charters within a school district,” Funk said via email.

The California Charter School Association, in its statement, said charters should not be held responsible for school districts’ financial woes.

“Local districts must own their role as fiscal stewards responsible for their budgets and stop ignoring the hard decisions that lie ahead — like crushing unfunded pension liabilities or underused facilities — and come up with a range of solutions that ultimately benefit all public students,” the statement says. “The methodology in this report is deeply flawed, draws irresponsible conclusions and shows a lack of understanding of district financials and only serves as a distraction.”

Though In The Public Interest’s representatives said Lafer’s research was independent, the California Charter School Association said it is “far from impartial,” according to its statement. The think tank — a project of the Partnership for Working Families nonprofit — researches government contracts and other public-private partnerships, and has published studies and information on the impacts of charter schools before.

The Partnership for Working Families is based in Oakland and advocates for workers’ rights and social justice, and is funded in part by labor unions AFL-CIO, the International Brotherhood of Teamsters, and the International Union of Painters and Allied Trades.

U.S. Department of Labor records show Lafer has in the past worked for an Oregon chapter of the AFL-CIO as a “strike coordinator.”

Labor unions that represent teachers and school workers have historically rallied against charter schools.

David Castillo, executive director of the Oakland Charters nonprofit, which advocates on behalf of charters schools in Oakland, was not surprised by the report, given the ongoing back-and-forth between unions and charter school groups. He hopes the two sides can work together.

“We have great schools in the district and great schools in the charter sector. What we need to focus on is expanding those programs throughout the city and at the same time making sure we’re operating efficiently,” Castillo said.

Oakland Unified Superintendent Kyla Johnson-Trammell said in an email the report is an important first step in understanding all the factors that affect school districts’ fiscal stability.

“The report focuses on costs and sustainability, but we also want to make sure that no matter the cost, we are always working to provide a quality education for all students,” Johnson-Trammell said.

During the 2016-17 school year, Oakland Unified had the highest concentration of charter schools in the state: 30 percent of Oakland students were enrolled in charter schools, according to the report.

“If Oakland weren’t losing $57 million per year, it would be possible to reduce class sizes to 18 students per class in all its elementary schools and also double the number of nurses and guidance counselors in its schools,” the report says.

Oakland Unified is in the middle of a budget crisis caused by several factors, including declining enrollment. The school board voted in December to cut $9 million from the district’s mid-year budget

Johnson-Trammell said she hopes the report and others like it sway decision-makers to create or reform public school policies. Analysis into the impact of charter schools on traditional public schools can help them better understand the “financial realities facing public school districts,” she said.

“As a district with roughly 30 percent of students enrolled in charters, we feel we have an important role in ensuring all students receive a quality education,” she added.