A strict requirement that schools keep up their spending on special education year to year may have unintended consequences, federal investigators say.

Under the Individuals with Disabilities Education Act, states and schools in most cases must maintain or increase their funding for special education services each year. Those that do not meet the spending requirement known as maintenance of effort without obtaining an exemption from the U.S. Department of Education can lose out on federal dollars.

The mandate has been in the spotlight in recent years as states struggled during the recession to keep up with their commitments from prior years.

In a report this week, the Government Accountability Office said that nearly all school districts complied with the mandate as of the 2012-2013 school year — the most recent for which data is available — though many reported that they had difficulty doing so. But, GAO warned that the rigid spending requirement could be stifling innovation in special education.

State and school district officials surveyed by GAO told the agency that “because the (maintenance of effort) requirement lacks flexibility, it can discourage districts from altering their baseline of special education spending, even when doing so would benefit students with disabilities or result in more efficient delivery of the same services.”

Specifically, educators told Congress’ investigative arm that having to meet maintenance of effort requirements can leave them skittish about introducing pilot programs or expanding services that might necessitate only a temporary funding bump.

Federal investigators cited the Education Department for further hindering districts with “evolving policies” on maintenance of effort and monitoring and feedback that’s often delayed years.

GAO said in its report that Congress ought to consider ways to make maintenance of effort more flexible to encourage innovation and efficiency.

“A less rigid (maintenance of effort) requirement would allow districts more latitude to adjust their spending at the margins — focused on providing the best services to address the most pressing needs of students with disabilities — while mitigating the effects of unintended consequences,” the agency found.

In a response to GAO, the Education Department called maintenance of effort a “crucial protection” for students with disabilities and agreed with investigators’ recommendations to improve technical assistance efforts and increase the timeliness of monitoring and feedback.

Officials with AASA, which represents school superintendents across the country, applauded GAO for encouraging a less rigid standard.

“IDEA must provide districts with the flexibility to ensure they are not wrongly penalized for changes in their special education funding levels that in no way impact the provision of special education to students with disabilities,” said Daniel Domenech, the group’s executive director.