A federal civil rights probe has found that administrators at Boston Latin, the nation's oldest public school, failed to adequately respond to racist threats made to a black student by a classmate.

U.S. Attorney Carmen Ortiz on Monday announced the civil rights violation and other findings from her office's monthslong probe. The federal investigation was prompted by a request from the NAACP and other civil rights groups.

Ortiz says the school district is imposing measures to ensure racial discrimination complaints are handled appropriately going forward. The school district, the NAACP and the ACLU didn't immediately comment.

In November 2014, a male student allegedly used a racial slur and threatened to "lynch" a black female classmate. A previous school district investigation also concluded the incident was mishandled.