LISLE, Illinois — A Catholic school in suburban Chicago rescinded a job offer to a coach after learning that she was in a same-sex marriage, the woman’s supporters claim.

About 40 alumni, parents and students met outside Benet Academy in Lisle on Monday to support the woman who was to become coach of the girls lacrosse team. Thousands more have signed an online petition.

“By rejecting a talented potential staff member on the basis of whom she loves, you have utterly failed to uphold the principles of dignity and charity that you purport to practice as Christian institution,” the petition said. “We are ashamed of your narrow interpretation of Christian morality.”

Benet declined to speak directly about the coach. The Catholic Church is opposed to same-sex marriage.

“Benet Academy respects the dignity of all human beings to follow their conscience and to live lives of their choosing,” spokeswoman Jamie Moss said. “Likewise, as a Catholic school, we employ individuals whose lives manifest the essential teachings of the church in order to provide the education and faith formation of the young people entrusted to our care.”

Colleen Savell, an assistant lacrosse coach at Benet, said the coach has won two state championships in Pennsylvania.

“The girls look up to her,” Savell said. “She would just be an outstanding person to be a high school coach here.”