Civil rights advocates on Monday asked the U.S. Supreme Court to review a Texas law requiring public schools to display the Ten Commandments, teeing up a potential new test of state-sponsored religious expression in classrooms.

Posters featuring the Ten Commandments began going up almost a year ago in classrooms across Texas, which educates about 5.5 million students. An appeals court earlier this year cleared the way for Texas’ law and one in Louisiana, and similar laws have been passed in Arkansas and Alabama.

“This is an issue of nationwide importance because a number of states have been considering these laws in recent years,” said Heather Weaver, an attorney with the American Civil Liberties Union.

Over two dozen Texas families represented by the ACLU and other groups petitioned the nation’s highest court to hear their challenge after the conservative-leaning 5th U.S. Circuit Court of Appeals in April upheld the Texas law in a 9-8 ruling.

“We would like for the Supreme Court to make clear that singling out Scripture for display in public schools is a violation of the First Amendment,” Weaver said.

The office for Texas Attorney General Ken Paxton did not immediately comment Monday.

In the families’ Supreme Court brief, their attorneys argue that the law violates basic First Amendment principles governing the separation of church and state.

“The question of whether a state may impose scripture on impressionable, captive-audience children — for nearly every hour of every school day, for up to (13) years — implicates the most fundamental guarantees of the First Amendment and our Nation’s highest ideals,” they wrote.

The New Orleans-based 5th Circuit reversed lower federal court rulings that had blocked some Texas school districts from putting up the posters.

Republican Gov. Greg Abbott signed the law, which took effect last September. Because Texas’ law only requires districts to hang the Ten Commandments if they are donated, conservative groups and individuals began dropping off boxes of posters at campuses across the state as the school year began last year.

“No child is made to recite the Commandments, believe them, or affirm their divine origin,” the 5th Circuit’s ruling says.

In 1980, the U.S. Supreme Court ruled that a similar Kentucky law violated the establishment clause of the U.S. Constitution, which says Congress can “make no law respecting an establishment of religion.” The high court found that the law had no secular purpose but rather served a plainly religious purpose.