A back-to-school prayer service was cancelled at the public school in Mississippi and moved to a church after an atheist group sent a letter, claiming that the event was an endorsement of religion in violation of the U.S. Constitution.

The Oak Park Elementary School in Ocean Springs was supposed to host a back-to-school prayer service on Aug. 2.

The atheist group Freedom From Religion Foundation (FFRF) said the Ocean Springs School District partnered with local churches for the event.

FFRF sent a letter to Superintendent Bonita Coleman-Potter asking her to cancel the event, saying it is "a blatant violation of the Establishment Clause" under the First Amendment.

"It is well settled by the courts that public school employees may not lead, direct or encourage students to engage in prayer. The Supreme Court has continually struck down formal and teacher or school-led prayer in schools," said FFRF's Rebecca Market in the letter.

The group stressed that Coleman's participation in the event made it questionable.

"The prayer event is an especially egregious violation," said Market . "The event is school-sponsored and school-promoted. Indeed, you, as the school superintendent, are promoting the religious ritual. It does not matter that this event occurs outside normal school hours because prayers at other after-school events such as football games and graduations have been found unconstitutional by the U.S. Supreme Court."

She also claimed that "partnering with local churches to put on this prayer service also constitutes excessive entanglement between government and religion."

Coleman's participation was an indication that the school district "endorses the message being given," the FFRF senior staff attorney added.

After receiving the letter, the school district decided to transfer the event to a church.

To avoid a court case, Coleman and Rev. M.M. Kirby of St. Paul United Methodist Church decided to move the back-to-school prayer to the First Baptist Church in Ocean Springs, the Mississippi Press reported.

Coleman would not participate in the prayer event. She said it costs the district $150 an hour every time a lawyer is hired.