The Dover School District says it is investigating an incident of what it's calling "extreme racial insensitivity" at Dover High School.
A video posted on social media shows students singing a song about the Ku Klux Klan and violence against African Americans to the melody of "Jingle Bells." It was part of an assignment for an 11th grade history class.
William Harbron is Superintendent with the school district.
"Our goal here, with this situation, is to make sure this never occurs again," Harbron said. "We want to make sure all the students in our district -- regardless of race or background -- are accepted and honored and respected in our schools."
Harbron says students didn't know they were being filmed but that there was a teacher in the classroom during the incident.
He says families and the school community will be updated as the district addresses the matter.