A virulent anti-Christian group is demanding that Bible classes in multiple North Carolina.

Cleveland, Woodleaf and Mount Ulla Elementary Schools in the Rowan-Salisbury School System have 45 minute classes that parents may opt out their children if they do not wish them to receive instruction.

The anti-Christian Freedom From Religion Foundation sent a threatening letter after another “anonymous” individual complained that the school was teaching the Bible.

“It is irrelevant that parents may excuse students from the elementary Bible classes,” the anti-Christian group wrote. “Suggesting that children who do not wish to be subjected to religious activity at their school should be segregated from their classmates is reprehensible. … It makes no difference if some parents would like the Rowan-Salisbury School system to teach the Bible as fact to its students.”

The school district said they are looking into the matter but refused further comment.