School officials are investigating “an incident of extreme racial insensitivity” at a New Hampshire high school after students were filmed singing a KKK-themed Christmas carol.

The song was performed by Dover High School students for “a classroom assignment dealing with [the] reconstruction period in American history,” the school district’s superintendent, William Harbron, said in a letter Monday.

According to NBC, the 11th-grade students, who were unaware that they were being recorded, had been assigned to create a jingle based on the era.

FACEBOOK SCREENSHOT The "incident of extreme racial insensitivity" is currently being investigated by school officials.

Lyrics, according to multiple outlets, included “KKK, KKK, let’s kill all the blacks,” sung to the tune of “Jingle Bells.”

“We are deeply concerned that an event such as this could occur and understand the emotion and concern that this event will create for our students, families and staff,” Harbron said.

“Administration from Dover High School and the District are working with students and the school community to respond immediately and effectively to this racial insensitivity.”

The Ku Klux Klan was founded after the Civil War in 1866 as a league of white terrorists bent on suppressing and victimizing the newly freed slaves.