For the past several years, the Education Department has received thousands of civil rights complaints: victims of alleged sexual assaults saying their universities mishandled their cases, blind students encountering inaccessible textbooks, girls basketball teams seeking equal access to gymnasiums.

In an effort to reduce a backlog of cases, the Education Department under Secretary Betsy DeVos began dismissing complaints that placed “an unreasonable burden” on the department. And it dispensed with cases filed by the same person or group against multiple institutions — a tactic commonly used to show a pattern of violations.

But three civil rights groups allege in a lawsuit that by doing so, the Education Department may be unlawfully dismissing complaints even if students or their families provide ample proof of discrimination. They say this closes a critical avenue for students — particularly those with disabilities — to defend their right to an education in classrooms and on college campuses.

The NAACP, the National Federation of the Blind and the Council of Parent Attorneys and Advocates — which represents lawyers that advocate for students with disabilities — sued Thursday in federal court, saying the new procedures violate the law and are “arbitrary and capricious.”

“Effectively, they’ve reserved the right to dismiss cases just because they’re hard,” said Brad Berry, general counsel for the NAACP. He said the agency is flouting its responsibilities in the name of efficiency. “The objective is not docket maintenance. The objective is doing justice.”

Elizabeth Hill, an Education Department spokeswoman, said she could not comment on pending litigation. But she defended the changes to the agency’s Office for Civil Rights (OCR), saying the new procedures were “the product of many months of collaboration among career investigators and career managers reflecting OCR employees’ commitment to robustly investigating and correcting civil rights issues.”

The office “will dismiss complaints if they’re part of a pattern of similar complaints filed by an individual or a group. This provision is intended to permit [the office] to remain active in every type of discrimination subject matter while retaining discretion to engage in technical assistance efforts where appropriate,” Hill said.

DeVos has faced scrutiny for her handling of civil rights matters. Not long after she was confirmed as secretary, she and Attorney General Jeff Sessions rolled back Obama-era guidance that directed schools to allow transgender students to use restrooms that align with their gender identity. And they halted investigations into complaints filed by transgender students over restroom use.

Later, DeVos rescinded other guidance that outlined how schools and universities should investigate allegations of sexual assault.

She also sought to cut staff from the OCR, a change that would require investigators to take on much larger caseloads.

The OCR began changing its procedures as early as a year ago, when interim head Candice Jackson directed investigators to no longer identify “systemic” problems. That practice allowed investigators to probe whether a complaint filed by one student resulted from a broader problem that required a sweeping remedy.

This year, the department rewrote the manual that outlines how staffers should investigate complaints, requiring investigators to immediately dismiss complaints that posed an “unreasonable burden” on department resources. It also eliminated an appeals process.

While Hill said the department would still accept complaints filed by third-party groups, the provisions worry civil rights advocates, who often file multiple complaints on behalf of groups of students to spur investigations of suspected widespread discrimination. They worry that the new provisions could allow the department to ignore serious violations of anti-discrimination law.

“Our students already face huge hurdles to receive . . . the supports and accommodations they’re entitled to under the law,” said Denise Marshall, executive director of the Council of Parent Attorneys and Advocates. Marshall called the OCR “a lifeline” for students with disabilities. “This put an insurmountable hurdle in front of them by unlawfully taking away their right to issue a complaint or to appeal a decision regarding discrimination.”

Marcie Lipsitt, a Michigan advocate for students with disabilities, said she saw the impact of the changes almost immediately. Lipsitt said that since 2016, she has filed about 2,400 complaints against schools and state education departments that have websites inaccessible to those who are blind, deaf or have motor impairment — including schools for the blind.

Previously, the department investigated her complaints and often took action, such as compelling officials to update websites. Since the changes have been implemented, her complaints have been dismissed en masse, she said.

“Those revisions are unlawful, and they have stark implications for all civil rights and Americans,” Lipsitt said.