WASHINGTON — This article is a collaboration between ProPublica and The New York Times.

A year and a half after receiving a detailed complaint from tribal leaders, the Education Department plans to investigate their accusations that the Wolf Point School District in Montana discriminates against Native American students.

In a Dec. 28 letter, sent hours after The New York Times and ProPublica published an investigation into racial inequities in the district, the department’s Office for Civil Rights notified the lawyer representing the tribal executive board of the Fort Peck Indian Reservation in eastern Montana that it would look into the complaint. The board includes members of the Assiniboine and Sioux tribes. Native American and mixed-race students make up more than three-quarters of Wolf Point’s enrollment.

According to the letter, the investigation will focus on whether Wolf Point schools discipline Native students more harshly than white students, shunt them into remedial programs without appropriate cause, and deny them special education evaluations and services.

The department said it would also examine whether the district failed to respond to a parent’s accusations that a Native student was racially harassed. The student was not identified in the tribal complaint or in the letter.