Oklahoma’s top education official ordered public schools Thursday to incorporate the Bible into lessons for grades 5 through 12, the latest effort by conservatives to incorporate religion into classrooms.

The directive drew immediate condemnation from civil rights groups and supporters of the separation of church and state, with some calling it an abuse of power and a violation of the U.S. Constitution.

The order sent to districts across the state by Republican State Superintendent Ryan Walters says adherence to the mandate is compulsory and “immediate and strict compliance is expected.”