As the U.S. Department of Education fielded a record number of civil rights complaints last year, the agency said nearly half alleged some form of disability discrimination.

The Education Department’s Office for Civil Rights received over 4,800 complaints asserting violations of disability laws during the 2015 fiscal year, according to a report released this week.

Disability issues accounted for the largest group of complaints logged, representing 46 percent of the record-high 10,392 complaints received by the Office for Civil Rights, which is tasked with ensuring equal access and prohibiting discrimination based on race, color, national origin, sex, disability and age in education programs.

While the overall number of disability-related complaints dropped slightly compared to the 4,919 filed in 2014, the Education Department said that reports of inappropriate restraint and seclusion as well as issues related to Web accessibility for students with disabilities were both on the rise.

The greatest number of disability-related complaints lodged last year hinged on the right to a free, appropriate public education followed by complaints of retaliation and those centering on exclusion or different treatment.

Many complaints crossed over into more than one of the 18 categories of disability discrimination that the office tracks, the report said.

Over the course of the year, the Office for Civil Rights said it successfully resolved 4,655 of the disability complaints received. In addition to responding to individual complaints, the Education Department issued five guidance documents in 2015 addressing disability-rights issues in schools.

“OCR’s work over the last year has been absolutely pivotal to advancing the department’s goal to increase equity and opportunity for all students,” said U.S. Secretary of Education John King. “Through our guidance, technical assistance, data collection and investigatory work, the department’s message to the public is clear: We are committed to working with and supporting schools to protect students’ civil rights — and we will take action to secure those rights when necessary.”

The caseload handled by the Education Department’s civil rights office has nearly doubled in the last decade even as staffing levels have declined to a record low, the agency noted.