Louisiana Governor Jeff Landry on Wednesday signed into law a bill that makes the state the only one in the country to require displaying the Ten Commandments in every public school classroom.

The American Civil Liberties Union immediately announced it would sue to block the law, saying it violates the constitutional separation of church and state and a US Supreme Court ruling.

Landry signed the bill along with a package of others he said were designed to "expand faith in public schools."

"If you want to respect the rule of law, you've got to start from the original law-giver, which was Moses," Landry said at the signing ceremony.

In the Christian and Jewish faiths, God revealed the Ten Commandments to Hebrew prophet Moses.

Other measures would authorise the hiring of chaplains in schools, restrict teachers from mentioning sexual orientation or gender identity, and prevent schools from using a transgender pupil's preferred name or pronouns unless granted permission by parents.

Landry also signed bills that would expand tutoring for underperforming students, help improve maths skills, and impose fewer curriculum mandates on teachers.

Civil rights group ACLU and its Louisiana chapter along with Americans United for Separation of Church and State and the Freedom from Religion Foundation announced they would file a lawsuit to challenge the law that requires a specific text of the Ten Commandments be prominently displayed in all classrooms.

No other state has such a law, the groups said in a statement.

"Politicians have no business imposing their preferred religious doctrine on students and families in public schools," the statement said. (Reuters)