An extended family comes to terms with the gender transition of one of their own in director Gaby Dellal’s drama “About Ray.”

Elle Fanning stars as the titular Ray, a high-school student who’s ready to fully express how he feels inside. Written by Dellal and Nikole Beckwith, “About Ray” deals with the quotidian decisions that many trans youth go through — to change schools or not? how to explain trans identity to younger siblings? — as well as the specifics of Ray’s close yet fractured family situation.

“Why can’t she just be a lesbian?” wonders Ray’s grandmother, played by Susan Sarandon, in a line that’s surely been uttered in real-life homes. Thankfully for Ray, his mom, played by Naomi Watts, is a lot more understanding of his struggle and comes to his defense when mother and son are forced to reckon with his recalcitrant dad, whose signature the teen needs to undergo hormone therapy.

“About Ray” opens September 18.