To avoid further controversy, the American Civil Liberties Union of Mississippi has rejected a $20,000 gift intended to underwrite an alternate prom replacing one canceled by a local school district after a lesbian student demanded that she be allowed to attend with her girlfriend.

The gift, to sponsor one of several privately sponsored alternate events, came from the American Humanist Association, an advocacy group whose mission is to promote “good without God.”

“Although we support and understand organizations like yours, the majority of Mississippians tremble in terror at the word ‘atheist,’ ” Jennifer Carr, the fund-raiser for the A.C.L.U of Mississippi, wrote in an e-mail message to Roy Speckhardt, executive director of the humanist group.

According to Matthew Sheffield, a spokesman for the Mississippi Safe Schools Coalition, the organization arranging the event, the A.C.L.U. of Mississippi did not have authority to decline the gift.