For the students at a remote boarding school for Kurdish boys, survival is a matter of course, particularly during the frigid depths of winter. The meals are meager, the heating doesn’t work, and even the principal’s car won’t start. Even if it did, he can’t afford snow tires, rendering his vehicle useless in the thick blanket of snow that covers the Eastern Anatolian mountains. All one can do is endure, and fifth-grader Yusuf (Samet Yildiz) has learned that keeping a low profile will spare him the exacting punishments the teachers dole out on his more rambunctious classmates. But when he discovers his best friend Memo (Nurullah Alaca) gravely ill one morning, Yusuf is forced to make himself visible to ensure that Memo is cared for. What unfolds in “Brother’s Keeper,” the latest, very carefully composed feature from Turkish director Ferit Karahan, is a tough lesson for Yusuf about the ruthless inertia of bureaucracy, which can feel far chillier than the temperatures outside.