Good luck naming high school movies that aren't in some way about rebellion. Frederick Wiseman's vérité triumph High School? Maybe Air Bud 2: Golden Receiver? It's a short list.

So how does one create teenage conflict when the would-be authority figures are open-minded Southeast Portland parents? The characters in the new Portland coming-of-age indie Young Hearts have the same question.

"They're trying so hard to be progressive that there's nothing to rebel against," explains freshman Harper (Anjini Taneja Azhar) to sophomore Tilly (Quinn Liebling), her love who just yesterday was merely her brother's best friend.

Even though they filmed in their hometown, sibling directors Sarah and Zachary Ray Sherman, who attended La Salle Catholic College Preparatory in the early 2000s, can't personally relate to that high school experience. On the contrary, Young Hearts was a product of recent observation.

"So much of this was born out of my spying on teenagers everywhere I went," says Sarah, who directed much of the movie on her own Southeast Portland street, with some exteriors at Franklin High School.

That anecdotal research impacts the way teenagers communicate in Young Hearts, which played at the Portland International Film Festival back in March as Thunderbolt in Mine Eye before its renaming for distribution. By any name, the film is distinctly Gen Z. Nobody in Can't Hardly Wait (1998) asks a crush about their political convictions as an ice breaker.

"I remember a time when I had my toddler at this park and this group of teenagers was having a conversation about abortion rights," Sarah says. "That was not a conversation I was having at this age. When I was a teen, there was such a bubble between us and adults. I feel like it's different now."

Ironically, though, the timeless, ineffable difficulty of almost-not-quite adulthood still drives the tension in Young Hearts. A burgeoning sexual relationship between Harper and Tilly (ages 14 and 15) is incredibly normalized and non-exploitative by any Hollywood standard but still collides with the truth of being too young.

"Some people involved [in the movie] were like, 'Is this too much?'," Sarah says, noting the plethora of high school movies that depict sex between older high schoolers. "Teenagers have sex earlier than that too. Not all, but they do. And it doesn't have to be this dirty, shameful thing that results in pregnancy."

Leading off the Zidell Yards reprise of the Portland International Film Festival on Oct. 1, Young Hearts is slated for national and international release on Feb. 14. According to Zach, a Los Angeles actor and DIY director, its acquisition out of Slamdance Film Festival by Blue Fox Entertainment owes much to Mark and Jay Duplass serving as executive producers.

"We're just so lucky they're able to funnel and fast track us into the system," he says. "I think it's unheard of that you shoot a movie for under 40K and still hit these mainstream channels."

The Duplasses primarily responded to the authenticity of his sister's script, Zach says, as Young Hearts won a 2018 contest to be shepherded by the Safety Not Guaranteed (2012) and Skeleton Twins (2014) producers.

Authenticity in Young Hearts boils down not just to what's said, but the credible trouble the kids have saying it. The characters feel 15 because Liebling actually was, while Taneja Azhar played 14 at 18. Zach encountered both performers while acting with them on the Oregon-shot Netflix series Everything Sucks!, and their facility with adolescent ticks is undeniable. Saying goodbye is an odyssey, walking together an unsteady waltz, and both constantly prod "What?" at the other's unspoken thoughts.

"The biggest thing for me was rhythm and timing. And more awkward! More discomfort!" says Sarah with a laugh, adding that the raw ohs and ums eventually came off as overwhelmingly real in one editing round.

As far as the Shermans' sibling dynamics during their two weeks of onset co-directing, Zach calls it a blur, with an instinctual, all-consuming approach that would hopefully make the Duplasses proud.

"There were a few laughable moments where we'd yell cut, Zach would go up to one actor, I'd go up to the other one, and we'd tell them conflicting things," Sarah recalls. "And then they're like, 'Wait, what?' And I'm like, 'Goddammit, Zach.'"

SEE IT: Young Hearts screens at the Cinema Unbound Drive-In at Zidell Yards, 3121 SW Moody Ave., on Thursday, Oct. 1. 7 pm. $35-$55.