SNELLVILLE, Ga. — The principal of a Georgia high school where members of a marching band spelled out a racist slur with their instrument covers during a halftime show says the four students planned it as a "joke."

WSB-TV reports that Principal Bo Ford of Brookwood High School says in a letter to parents that three seniors planned the stunt. 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. He says they knew the slur was "not acceptable."

The students will be disciplined.

Normally the band uses the instrument covers to spell out the mascot Broncos. But last Friday the four students instead spelled a slur insulting black people. Ford apologized Saturday in a letter to parents and the community.