LOS ANGELES — When two boys were enrolled at a Roman Catholic school in Southern California at the start of the school year, word quickly spread that they were the sons of a gay couple.

Parents of other children at St. John the Baptist School in Costa Mesa demanded the boys be removed from the 550-student elementary and middle school. Eighteen parents wrote a letter complaining about the boys' presence and arguing that their admission violated Roman Catholic doctrine on homosexuality.

The case, along with a similar one at another Roman Catholic school, has raised questions about the church's policies regarding the education of children of same-sex couples.

In the California case, the parish's pastor agreed to keep the two adopted sons of the gay couple in school. But in the second case, in Eugene, Ore., school officials refused to admit the adopted daughter of two lesbians. The mothers have sued the parish and school officials.

Experts and advocates for gays and lesbians think that such incidents are more widespread and that there will be a growing number of such cases as the number of same-sex couples increases. According to the 2000 census, an estimated 594,000 same-sex households could be found in the country; about 301,000 were male couples and about 293,000 female couples.

The Rev. Jim Schexnayder, resource director for the National Association of Catholic Diocesan Lesbian and Gay Ministries, said he was aware of many such confrontations in Roman Catholic churches across the country but was not at liberty to discuss specifics.

He said that in most cases, the disputes were resolved quietly and favorably for the children, who were allowed to attend classes.

The views of other parents were at the core of the dispute at St. John the Baptist School in Costa Mesa. The two boys involved have not been named publicly and neither have their parents, who have declined interview requests.

But the objecting parents said they thought their children could not receive full-fledged instruction on faith with the two boys in the school. They said they could not see how a teacher could fully explain the church's policies on homosexuals without causing the two boys anxiety about their fathers.

But the pastor, the Rev. Martin Benzoni, said the right of the children to an education was paramount and let the boys stay.

Schexnayder said the sincerity of the families' faith should determine the admissions policy, which differs from parish to parish. He noted that some Roman Catholic schools admit non-Catholics and non-Christians, while others admit only Catholics.

In the second case, Lee Inkmann and Trish Wilson tried to enroll their adopted daughter in kindergarten at the O'Hara Catholic School in Eugene.

At the start of August 2003, Inkmann went to the school to seek information that could help her decide if she wanted to enroll her daughter, according to a complaint filed in Circuit Court in Lane County, Ore. When the tour was over, Inkmann told Principal Dianne Bert that the child's other parent was also a woman.

"Defendant Bert became upset and said the school had never enrolled an 'out' gay family before," the complaint states.

The parents reportedly were informed that the girl would not be admitted because her having two mothers would be too confusing for other pupils. The complaint states that plaintiffs were also told that the same-sex couple's living arrangement was contrary to Vatican teaching and that the school needed to adhere to papal edicts.

The two women, who are seeking compensation of up to $550,000, declined to be interviewed.

Martha Walters, their attorney, said that under local ordinances the school, although private, is a place of public accommodation. "It is like a restaurant," she said.

Bud Bunce, a spokesman for the Roman Catholic Archdiocese of Portland, said he could not comment.

Gay and lesbian advocates said they expect church-school access to be a growing cause of concern. "All parents, gay or straight, want a quality education for their children," said David Tseng, an attorney who has worked with Parents, Families and Friends of Lesbians and Gays. "We are at the cutting edge of a civil-rights movement."