Janice K. Jackson, chief executive of Chicago Public Schools, wrote in a letter that the district is working to correct the problems. (Charles Rex Arbogast/AP)

The U.S. Education Department said Thursday that it had found “tragic and inexcusable” conduct by Chicago Public Schools in handling sexual harassment and violence complaints, detailing systemic failures to protect children.

The department’s four-year investigation followed complaints from two students — one who alleged assault by a teacher, another by a large group of students — and was expanded to find widespread failure by the school system to address the allegations.

The district — one of the nation’s largest — failed to provide services or remedies to those filing complaints, did not tell them the outcomes of investigations and did not take effective action to provide a safe environment, the Education Department said.

Kenneth Marcus, the Education Department’s assistant secretary for civil rights, said the investigation was the largest of its kind and called the findings “deeply disturbing.”

“The Chicago Public Schools have inexcusably failed, for quite some time, to provide their students with the basic protections required by law,” he said. “We cannot permit this to occur in Chicago or anywhere else.”

In 2018, the Chicago Tribune found more than 500 police reports of sexual assault or abuse of a child inside a Chicago public school over the prior decade. Soon after, the agency appears to have expanded its investigation.

That investigation included reviews of 2,800 complaints of student-on-student harassment and 280 adult-on-student allegations over four years.

The original probe was sparked by two cases.

In the first, a student said a teacher frequently commented on her body and appearance, bought her food and gifts, texted, and emailed her from a private account he used to send photos of himself. He also professed his love. Eventually, he took her out, bought her alcohol, kissed and fondled her and forced oral sex, even as she cried and begged him to stop, the Education Department said.

In the second complaint, a student said she was surrounded by 13 boys on her way home from class, some of whom she recognized from school, forced into a vacant building and repeatedly raped.

In both cases, and many others, the civil rights office concluded, the Chicago schools mishandled the complaints.

Under the settlement announced Thursday, the Chicago school system agreed to give those who believe their complaints were mishandled the chance for a second, independent review. It also promised to review the actions of district employees who failed to properly respond to allegations. And it promised changes in its procedures for handling Title IX investigations.

In a letter to “friends and supporters” on Thursday, the chief executive of the Chicago schools, Janice K. Jackson, said the district is already working to correct the problems. She said the events described in the federal report occurred before the district began to implement new protections for students.

“These were tragic incidents in which some students did not receive the comprehensive support they deserved. As a district, we have been working to ensure no student ever goes through that again,” she wrote.

Under Title IX, school districts can lose federal funding if they discriminate on the basis of sex in their programs or activities. Under that law, districts are obligated to respond promptly and equitably to allegations of sexual harassment, including sexual assault and violence.

Withholding federal funding would be an option if the district fails to comply with the order, Marcus said.