MIDDLETOWN, Conn. — The controversy began, as many do these days, with an online petition.

A senior at Mercy High School in Middletown, an all-girls Catholic school, wanted to bring another girl as her date to the prom. The school’s longstanding policy was clear: Girls could go with friends or bring a boy as a date.

More than 1,800 signed the student’s “Let Girls Take Girls To Prom” petition on Change.org, and the ensuing debate showed the increasingly complex position the Catholic church and its schools are in.

Traditional Catholic policies remain, but Pope Francis is setting an agenda of greater flexibility and understanding. And though the issue is over for this prom season at Mercy, some alumni are pushing the school to change.

In a statement made after the petition started, Mercy President Sister Mary McCarthy acknowledged that LGBT issues have been a topic of consideration for the school. But families understand students attending the school will be expected to abide by official Catholic teachings, she said.

“It is a very fine balance, for sure,” said Norwich Diocese spokesman Michael Strammiello. “All of this is taken very seriously by the people in charge of the school and in charge of the students. They’re not closed-minded to all the concerns being brought forward.”

Strammiello said Catholic schools must look to the church for such decisions.

“Until there’s such time of significant policy movement, we’re in a place that all the stakeholders are familiar with,” Strammiello said. “Policies established over a long time don’t change overnight.”

The church is “caught between two impulses” lately, said Harold Attridge, a professor and former dean of the Yale Divinity School. Pope Francis and individual churches have been increasingly more tolerant of divorce and homosexuality, and the pope recently said he was open to exceptions to the church’s prohibition on marriage for priests.

Attridge said the Catholic Church and its schools are in a complex position. Pope Francis’ emphasis on openness and inclusion has appealed to young people, but traditional policies remain, he said.

“Catholic schools would find themselves in a difficult position if they said anything goes, or same-sex couples are fine,” Attridge said. “Leaving open the possibility that it’s not a moral choice, it’s natural, is different than saying the rules no longer apply. The way these two things have been squared in most Catholic circles is if it’s a fact that you’re attracted to members of the same sex, the norms of sexual behavior still apply, so if you’re gay, you’ve got to be celibate.”

In general, church teachings say impulses themselves are not sins but acting on those impulses is a sin. Attridge said a Catholic school allowing same-sex dates may be seen as condoning students acting on impulses that are officially against church teachings.

“Many argue the church ought not to change its principles because society has changed, and that maybe society ought to change back,” Attridge said. “At the same time, the leadership of the church would say we want to be as welcoming as we can to all types, but we have our principles.”

The initial petition was published the last week of February, but the student closed it a few days later. A follow-up petition by Westbrook resident Colin Bennett seeking an apology and change in policy from Mercy went up a few days later, gathering 1,600 more supporters. Bennett has no connection to Mercy, but said he felt the school owed an apology to the student and the community.

In a statement March 7 in response to media questions, McCarthy, who was the school’s principal for years before becoming its president in 2012, said in “adhering to the teachings of the Church,” the school requires its students to attend the prom “alone or in the company of a friend or friends of their choosing” but that “the expectation has been that a Mercy student’s date be male.”

Mostly, the school expects that male date to be a student from Xavier High School, the all-boys Catholic high school in Middletown.

“Our mission … is guided by the overarching tenets and teachings of the Catholic faith. Mercy expects that those who elect to attend the school do so with an understanding and desire to abide by these principles,” McCarthy said.

Victoria Scott, a 2013 Mercy graduate from Oxford attending a university in upstate New York, was among former students who weighed in on the Mercy senior’s request. She and others started a website around the social media hashtag #wePROMise and are awaiting a response from Mercy, the Norwich Diocese, the Hartford Diocese and the Vatican, which have all received the petition.

“I would like to know what the issues are that would take so long to make a decision,” Scott said. “We’ve brought this issue to light, waiting for a response, and the ‘why’ hasn’t been answered.”