ST. PAUL — Minnesota’s legislative auditor detailed Wednesday how fast-rising special education costs are hampering the ability of school districts to reach other education goals, such as reducing class sizes.

An audit delivered to lawmakers urged them to find ways to ease the special education burden on school districts, whether it’s supplying more state money or revising regulations the state sets beyond federal requirements.

“We concluded that the funding arrangements for special education contain disincentives for controlling spending,” Auditor Jim Nobles wrote in his office’s report.

The report says that the median school district now devotes one-third of its basic education budget to special education. That’s a 40 percent jump between 2000 and 2011 when adjusted for inflation. It’s money that would otherwise be put toward general education costs.

Roughly 14 percent of the state’s public school students are in a special education program, which is up slightly from a decade ago. Special education can involve individualized learning programs for students with physical disabilities, speech and language impairments or about a dozen other disability categories.

Lawmakers are expected to debate the so-called cross-subsidy this year. The report suggests they also look at rewriting some state regulations. Several Minnesota laws exceed federal requirements, including the standards used to place children in those classes and workloads on teachers.

State Education Commissioner Brenda Cassellius said she is committed to making changes in special education to assist school districts without paring back the state’s obligation to serve the needs of students.

The audit, Cassellius said, “affirms what we have long known: Our state must do a better job of funding special education to meet individual students’ needs and to support the teachers who make a difference in their lives.”

Teachers union president Doug Dooher, of Education Minnesota, responded to the report with a plea for lawmakers to support Gov. Mark Dayton’s request for $125 million more in special education payments to schools.

“Special education has become an expensive morass of over-regulation that prevents many of our educators from doing what they do best — teach children with special needs,” Dooher said. “It’s time to make changes.”