Austin Metcalf 's dad ripped into pretty much everyone on his recent podcast appearance ... this time he's taking aim at the school superintendent, calling him a "bald-headed piece of s***." Jeff Metcalf went after the Frisco Superintendent on Sarah Fields ' "JinxedSip" podcast ... calling him "the most spineless, coward piece of s*** I've ever met in my entire life." He blasted the superintendent for allowing Karmelo Anthony to graduate high school after stabbing his son to death at a track