In Megan Park’s My Old Ass, Elliott (Maisy Stella) celebrates her 18th birthday by wandering off to a nearby forest with her two besties, Ro (Kerrice Brooks) and Ruthie (Maddie Ziegler), to do mushrooms. Meanwhile, her deflated parents (Maria Dizzia and Alain Goulem) look sorrowfully at the surprise birthday cake they prepared for her, wondering how much they’ll see of their daughter before she heads off to college in three weeks. It’s not that Elliott doesn’t love her family, or even her annoying brothers, Max (Seth Isaac Johnson) and Spencer (Carter Trozzolo), but the queer spitfire is yearning to break free—and to have the sorts of experiences that aren’t possible in the small Canadian town in which she was raised.

Refreshingly for a film that centers on a queer person, expressing her queerness isn’t among the experiences that Elliott can’t have here,...