SNELLVILLE, Ga. (CBS Local) — It was apparently meant to be a joke, but nobody seems to be laughing. Members of a marching band at a Georgia high school spelled out a racial slur last Friday with their instrument covers, WGCL reports.

Normally the band uses the instrument covers to spell out the mascot Broncos. But this time, the covers were used spell out a four-letter racial slur that starts with the letter “c.”

In a letter to parents, Principal Bo Ford of Brookwood High School said three seniors planned the stunt as a “joke” and a fourth student went along at the last-minute. Ford says two of the students are African-American, one is Asian and one is Hispanic and knew the slur was “not acceptable.”

“I am hurt and disappointed in these students and their actions that have stunned our community,” Ford wrote. “As you all know, this is not who we are.”

Ford said the four students involved, plus two more students who provided false information to school officials, will be disciplined.