Mash 1 banana in a medium bowl with a fork until no large lumps remain. Add oats, milk, ¼ cup yogurt, vanilla, chia seeds, cinnamon and salt; whisk until thoroughly combined, about 30 seconds.
Cover and refrigerate until the oats have absorbed the liquid and the mixture is thickened, at least 8 hours. Spoon about ⅓ cup of the oat mixture into each of 4 (8-ounce) jars; top each with 2 tablespoons of the remaining yogurt. Cut the remaining banana into ½-inch-thick slices; divide among the jars, arranging in an even layer over the yogurt. Top with the remaining oat mixture. Top with crushed graham crackers before serving.
