An atheist group has demanded that an Oklahoma school remove a poster from its main office–but the school district said “no.”

For the last 18 years, a poster based on a painting, “Faith in America” by Donald Zolan, has been displayed in the main office of Kenneth Cooper Middle School in Oklahoma City, Okla.

The Freedom From Religion Foundation recently sent a letter to Dr. Fred Rhodes, the Putnum County Schools Superintendent, arguing that the poster violates the establishment clause of the U.S. Constitution.

Freedom From Religion Foundation attorney Andrew Seidel wrote that the poster depicts “two children with their hands clasped in prayer, with an American flag background,” and as such is inappropriate material for a school.

“The meaning could not be more clear, real American children pray,” Seidel wrote.

Seidel then demanded that the poster be removed from the school and that he be informed in writing afterwards.

Putnam County Schools attorney Anthony Childers responded to the atheist group, writing that the poster does not “promote any particular faith and does not create coercive pressure on students who may see the image.”

Childers described clasped hands as a “non-sectarian symbol” that only refers to religion “in the most general sense.”

“We cannot agree that the poster displayed in the office is a per se violation of the Establishment Clause of the United States Constitution,”wrote Childers.

Childers added that the district will not be removing the poster.

In an email to Childers, Seidel called his response “insufficient” and threatened further action.