The Alliance Defense Fund, a Christian legal group, encouraged public school officials in Tennessee to continue recognizing Christmas despite recent threats from the American Civil Liberties Union.
"Urban legends about the offensiveness of Christmas are clearly out of sync with the American people, common sense, and the Constitution," ADF Senior Counsel David Cortman affirmed in a statement.
"The ACLU's conclusions are without merit and are part of a tired, worn-out, and disproven campaign of fear, intimidation, and disinformation," the letter read.
The ACLU warned public school officials not to focus on one religious holiday like Christmas during the holiday season, claiming such actions would be an unconstitutional endorsement of religion.
The group mailed a letter to 137 school superintendents across the Volunteer State, which read "Holiday celebrations that focus primarily on one religious holiday can result in indoctrination as well as a sense within students who do not share that religion of being outsiders to the school."
The ACLU said in a news release that it was responding to numerous complaints from families about such school activities.
Hedy Weinberg, ACLU executive director in Tennessee, said it is especially important for people to embrace the constitutional guarantees of the First Amendment in order to ensure that religious freedom flourishes.
The letter cites several U.S. Supreme Court decisions about the matter.
But ADF officials took exception to the ACLU's claim, saying no court had handed down such a ruling.
"No court has ever ruled that the Constitution demands school officials to censor Christmas carols, eliminate all references to Christmas, or silence those who celebrate Christmas," the ADF letter concluded.