The Justice Department announced a settlement Tuesday with a Tennessee county school district that the feds say engaged in a decades-long system of segregation involving African-American students.

The agreement, which ensures that the federal government will not take legal action against Robertson County Schools, alleges that the district built and expanded almost all-white schools "while leaving African-American students disproportionately in overcrowded schools with portable classrooms," the DOJ said in a statement.

Of the more than 5,000 students who attend the district's 11 schools, 72.5 percent of them are white, with African-Americans accounting for nearly one in 10 students.

It was not clear when the alleged segregation began, but The Tennessean reported that the school district did not follow a desegregation plan to which it had agreed in 1970.

Messages left with the DOJ and Robertson County Schools by FoxNews.com Tuesday afternoon were not immediately returned.

Under the agreement, a new elementary school set to open next year will be desegregated, overcrowding at predominantly minority schools will be "addressed," changes in student assignment to middle and high schools will be made to help desegregate, and "cultural sensitivity and competency training" will be provided to teachers and staff.

The district will be required to notify the Justice Department if it opens, builds, closes or renovates any school that would impact student assignments. The agreement also extends to charter schools in the county.

To ensure that Robertson upholds its end of the agreement, it will be required to provide the federal government with an annual report on its current enrollment demographics for the next five years, though the feds may request additional reports after 2020 to monitor compliance.

FoxNews.com's Karl de Vries contributed to this report.