Washington ? A skeptical Supreme Court heard a California atheist contend Wednesday that his 9-year-old daughter should not have to recite the Pledge of Allegiance at school because the words “under God,” part of the pledge for a half-century, violate the constitutional principle of separation of church and state.

During an hour of arguments, the justices raised repeated questions about whether Michael A. Newdow, the girl’s father, had the right to represent her before the high court. The justices — who begin every session with a clerk’s chant, “God save the United States and this honorable court” — also seemed to have serious doubts about the constitutional issue Newdow had raised.

“It’s not perfect, but it serves the purpose of unification” of the country, Justice David Souter said of the pledge. School officials argue that reciting the pledge is not a religious act, but a patriotic exercise designed to highlight the nation’s history and traditions.

The case is complicated because the girl’s mother, Sandra L. Banning, says she is a born-again Christian who does not object to her daughter’s reciting the pledge at school. Banning has sole legal custody of the girl, but Newdow has visitation rights and the right to consult with Banning over the girl’s education. Newdow and Banning never married.

In court Wednesday, Newdow, a lawyer who represented himself, said he was offended that the Elk Grove school district, where his daughter is enrolled, begins the day with a recitation of the pledge. He considers that state-sponsored religious indoctrination that is prohibited by the Constitution.

“The government is supposed to stay out of religion,” Newdow told the eight justices who heard the case. Justice Antonin Scalia did not participate because he had made a speech in which he expressed opinions about the case.

Justice Anthony Kennedy peppered Newdow with questions about how he could represent his daughter’s interests when he did not have custody and when a California court gave Banning the final say over the girl’s education.

Newdow responded that he had a right to express his opinions as the girl’s father, and as someone who is concerned about upholding constitutional principles.

Newdow sought to portray his daughter as a captive of school officials, who require students to recite the pledge. But Justice Ruth Bader Ginsburg said, “The child does not have to say the pledge with the words ‘under God.”‘

School officials said they allowed students to remain silent during the recitation of the pledge or to omit the words “under God.”

The court is expected to announce its decision by early summer.