An unmarried teacher is charging a Queens Catholic school with discrimination after she was fired for becoming pregnant out of wedlock.

The New York Civil Liberties Union yesterday filed a complaint with the federal Equal Opportunity Employment Commission on behalf of Michelle McCusker, 26, who was dismissed by the St. Rose of Lima School in Rockaway Beach last month.

The school, which is run by the Brooklyn Archdiocese, told Ms. McCusker it was firing her because she had violated the “precepts and doctrines of the Catholic church” by becoming pregnant out of wedlock. In the complaint, Ms. McCusker and the NYCLU claim the firing was an act of gender discrimination because the school’s policy can only be enforced against women.

“The school determined that Ms. Mc-Cusker violated Catholic doctrine only because they discovered her pregnancy,” an attorney for the NYCLU, Cassandra Stubbs, said. St. Rose of Lima couldn’t do the same for male employees, she said: “For example, does the school question its male employees about their sexual practices? How does the school punish male employees for engaging in nonmarital sex?”

The NYCLU said it had successfully fought a similar case in 2003, when the unmarried director of a Buffalo, N.Y., after-school program run by a Catholic charity was demoted after she became pregnant. After the group filed a complaint, the equal employment commission found that the charity had violated federal anti-discrimination laws. The charity agreed to adopt an employment policy that prohibited discrimination based on marital status or pregnancy, and the NYCLU said it was seeking a similar agreement from St. Rose of Lima.

The school referred questions about Ms. McCusker’s case to the Brooklyn Archdiocese. A spokesman for the archdiocese, Frank DeRosa, said teachers at the school are required, as outlined in a personnel handbook, to abide by Catholic teachings, both in words and actions. “This is a difficult situation for every person involved,” Mr. DeRosa said, “but the school had no choice but to follow the principles contained in the teachers’ personnel handbook.”

Mr. DeRosa disputed the NYCLU’s allegations, saying, “There is no discrimination involved.” When a violation of church teaching is made known, “whether it’s male or female, everyone is treated equally,” he said.

With her parents standing at her side, Ms. McCusker, speaking to reporters on her 26th birthday, cried as she recalled her short tenure at the school. She was hired in September to teach pre-kindergartners. A month later, she told the school’s principal, Theresa Andersen, that she was three months pregnant and did not plan to get married. Ms. Andersen initially “made it seem like it was fine,” and told her of a similar situation in which a pregnant teacher got married and was allowed to keep her job, Ms. McCusker said.

Two days later, however, the principal met again with Ms. McCusker and told her that she was being dismissed. Ms. Andersen also sent Ms. McCusker an official termination notice, which, the principal wrote, “was probably the most difficult letter I’ve ever had to write.”

“The way you live your life must witness the precepts and doctrines of the Catholic church,” Ms. Andersen stated in the letter. “When a situation becomes evident that a teacher’s life cannot witness what the Catholic church teaches, then termination of contract must occur.”

The principal went on to praise Ms. McCusker’s teaching ability and love of children, citing her “high degree of professionalism.”

“May your child be born healthy, knowing God’s loving care,” the letter concluded. Ms. McCusker, who lives in Nassau County, said she knew she could be fired when she told the school of her pregnancy, but the dismissal still came as a surprise. “I held the Catholic religion to a higher standard, I guess,” she said. “I thought the church was more forgiving than judgmental.”

Ms. McCusker is 18 weeks pregnant, she said, and the subject of pregnancy did not come up during her job interview in early September. She noted that had she chosen to have an abortion, which church doctrine strictly prohibits, she likely would still have her job. “They wouldn’t have known,” Ms. McCusker said.

The father of her child “was not involved with the pregnancy, and didn’t choose to be,” a spokeswoman for the NYCLU said. She would not identify him.