CHICAGO — A federal judge has ruled that a state law requiring a moment of silence in public schools across Illinois is unconstitutional, saying it crosses the line separating church and state.

"The statute is a subtle effort to force students at impressionable ages to contemplate religion," U.S. District Judge Robert W. Gettleman said in his ruling.

The ruling came in a lawsuit designed to bar schools from enforcing the Illinois Silent Reflection and Student Prayer Act. It was filed by talk show host Rob Sherman, an outspoken atheist, and his daughter, Dawn, a high school student.

Gettleman's ruling was not a surprise. He had already ruled in favor of Sherman in two previous decisions.

As passed by the Illinois General Assembly, the law allows students to reflect on the day's activities rather than pray if that is their choice and defenders have said it therefore doesn't force religion on anyone. But Gettleman backed critics such as the American Civil Liberties Union, who say the law is a thinly disguised effort to bring religion into the schools.

The "teacher is required to instruct her pupils, especially in the lower grades, about prayer and its meaning as well as the limitations on their 'reflection,"' Gettleman ruled.

"The plain language of the statute, therefore, suggests and intent to force the introduction of the concept of prayer into the schools," he said.

It remained unclear if Gettleman's decision would end the dispute or merely signal a fresh battle in a federal appeals court.

State Sen. Kimberly Lightford, D-Chicago, the chief sponsor of the legislation, said she hoped Illinois Attorney General Lisa Madigan would appeal.

"I strongly feel and I still believe that children should have a moment of silence at the beginning of the school day," she said by phone.

Madigan spokeswoman Robin Ziegler said the attorney general was reviewing Gettleman's decision and would have no immediate further comment.

Adam Schwartz, senior staff counsel of the American Civil Liberties Union, said the organization was pleased with the decision "to strike down a statewide law that coerced children to pray as part of an organized activity in our public schools."

Last year, a federal court threw out a challenge to a 2003 Texas law that allows children to "reflect, pray, meditate or engage in any other silent activities" for one minute at the beginning of each school day.

U.S. District Judge Barbara Lynn upheld the constitutionality of that law, concluding that "the primary effect of the statute is to institute a moment of silence, not to advance or inhibit religion."