The amount of money spent by school districts on special education varies greatly around the country, and some districts that spend less than others are getting better academic results from students, according to a study released Wednesday.

The study, sponsored by the conservative Thomas B. Fordham Institute, suggests that some districts are overspending on special education, which has become a growing segment of school budgets around the country.

If all districts spent the median amount on special education, it would save $10 billion a year, according to the study, which was written by Nathan Levenson, a consultant and former school superintendent.

Levenson gathered data from 1,400 districts representing more than one-third of K-12 students in the United States, making it the largest and most detailed collection of special education staffing and cost data available.

“There’s not a lot of research around spending in special education because I think it’s a topic that makes lots of people uncomfortable,” Levenson said. “No one wants to balance budgets on the backs of very needy children.”

Levenson focused on 10 pairs of school districts in five states — Florida, Massachusetts, Minnesota, Ohio and Texas. The districts that made up each pair were roughly the same size, with equal numbers of special education students and similar demographic characteristics.

In each pair, one district had higher achievement among its special education students while spending as much or less than the other district.

“People think intuitively that more spending must mean better outcomes,” Levenson said. “This paper shows that is just not true.”

The study did not explain why some districts spend less than the median but get better results. Levenson said that it boiled down to great teaching.

The single largest cost driver in special education is staffing, he said. In the study, the higher-spending, lower-achieving districts had 25 percent more teachers and paraprofessionals on their payrolls, Levenson found. A better plan would be to hire fewer but more effective teachers, he said.

Chester E. Finn Jr., president of the Fordham Institute, said school districts have been overly focused on spending for special education without enough concern about outcomes. “By and large, the districts in the study that spend less get better results for those kids,” Finn said. “That’s potentially a big deal.”

Special education is consuming an increasing share of school budgets nationwide. According to Levenson, special education represented about 21 percent of all education spending across the nation in 2005, or $110 billion, compared with 18 percent in 1996.

Locally, the District of Columbia has struggled to educate children with disabilities. A series of federal judges have found serious deficiencies in the District’s efforts, flagging problems with everything from transportation to the city’s ability to provide services to children in a timely manner.

The Fordham study recommends, among other things, that the federal government end the requirement that spending by states and localities on special education cannot fall below that of the prior year, except in certain cases.

Advocates for children with disabilities said they also support cost-effective budgets and want better academic results. But they said that special education historically has been underfunded.

“Repeatedly, every year, teachers, administrators, everyone says there isn’t enough funding to deliver the kind of services that are needed,” said Lindsay Jones, senior director for policy and advocacy at the Council for Exceptional Children, which represents special education teachers.

Jones said the study’s recommendation that the federal government stop requiring states and localities to maintain the previous year’s funding for special education is part of a campaign that began earlier this year with House Republicans. “Many attacks on maintenance of effort are coming about right now because of the fiscal crisis we’re in,” she said.