Back to School for Tatiana von Furstenberg and Francesca Gregorini

'Our friends called us the writers on bed rest.'

Befitting the pair’s past jet-setting as well as certain earthy peculiarities of boarding-school life, the tall tales that make up Tanner Hall take place in a school untrammeled by space and time. The aesthetic—all tweeds, embroidered curtains, and white-enameled-brick bathrooms—follows suit. Said Ms. von Furstenberg: “You don’t know where it is. It’s in America, but we tried to make it anywhere.”

“It could be England,” said Ms. Gregorini. “It could be—anywhere in Europe.”

“And it could be at any time!” continued Ms. von Furstenberg. “We intentionally put furniture and wardrobe from the 60s, 70s, 80s, 90s—because that’s what boarding schools look like! They have a frugality, a resourcefulness.”

The film follows a character, played by Rooney Mara of The Social Network and the forthcoming The Girl With the Dragon Tattoo, whose senior year at the boarding school Tanner Hall is derailed by the arrival of a seductive interloper, her childhood friend. There’s as much jealousy here as in Black Swan or All About Eve, and it’s compounded by the pressures of living together and the periodic interferences of a pair of house parents played by Chris Kattan and Amy Sedaris. The two directors both worked with the actors, who were, at the time of filming (excepting Mr. Kattan and Ms. Sedaris), young and untested women. The film was first shown in 2009, then shelved until this year’s studio release on the back of Ms. Mara’s burgeoning fame.

“I think it was a real benefit to be female filmmakers,” said Ms. Gregorini. “There was a level of trust there that the actresses were willing to go there with us. We’ve been where they are. It’s not like some guy saying, ‘Why don’t you lift that skirt a little higher?’”

Aside from the shared writing and talent nurturing, they divided their responsibilities.

“I’m a closet, wanna-be cinematographer,” said Ms. Gregorini, “so I spent a lot of time in the cinematography department.”

“And I don’t know a damn thing about shots,” said Ms. von Furstenberg. “She was envisioning the shots, and I was—”

“Decorating the rooms!,” said Ms. Gregorini.

“—decorating the rooms, and tackling the truths of the characters based on what they would be wearing. You know what I mean?”

“It’s a huge undertaking, directing a film,” said Ms. Gregorini. “To have a friend by your side before falling into that rabbit hole is huge.”

Even working as a duo, the two were unable to accomplish everything that needed doing. Ms. von Furstenberg’s mother helped out with costuming. Said the fashion scion: “We had three weeks of preproduction. Literally. And we have production values that look like we spent a lot of money. She didn’t do the costumes, but she delivered the uniforms, and they look amazing. The blazers are so well-cut. But it’s not like we had every resource available to us. She did it as a favor. We were pulling goodwill from everyone.”

It wasn’t just the costumes that were sourced unconventionally. “Our clothes, my curtains, my bedspread,” said Ms. Von Furstenberg, “literally is on-screen.”

Their resourcefulness, said Ms. Gregorini, made the pair more creative. They had, as Ms. Von Furstenberg put it, “a unified point of view” and created something on-screen that “was just externalizing a world that’s already inside of us.”

But what does that world look like? “Italy. Old World,” said Ms. Gregorini. “Tatiana and I share an emotional truth. Our understanding of the human condition is very shared, and we bring that to Tanner Hall, the challenges of being human, and the flawedness. And we’re quite open-minded. It’s not like a morality piece.”

“It’s really a family drama,” said Ms. von Furstenberg. “The parents are the teachers, and the girls are basically sisters. That’s their home. And I just had a midlife crisis recently. I’m out of it.”

“I’m not,” said Ms. Gregorini.