In “Bottoms,” a pair of teenagers start a fight club in their high school gym. The twist: The pugilists are lesbians, and they are whaling on each other — in the guise of self-defense — as a way to attract the hottest cheerleaders. (It’s a satire on many levels.)

The writer-director Emma Seligman had the idea and sold the script — to Elizabeth Banks’s production company — even before her feature debut, “Shiva Baby,” put her on the indie filmmaker map in 2021.

“I really love teen adventure movies,” Seligman said in a phone interview, “and giving queer kids the chance to be in that story.”

Seligman, 28, grew up in Toronto in a family of film buffs. “Everyone here is always just talking about movies,” she said. By 10, she was a judge at a children’s film festival; later she got involved with the Toronto International Film Festival. She studied the subject at New York University, where she met the two stars of “Bottoms” — Rachel Sennott (who…