At “Prom,” every couple has a story and no two are exactly alike. Several intersecting stories unfold at one high school as the big dance approaches; “Prom” portrays the precarious passage from high school to independence as some relationships unravel and others ignite. For Nova Prescott (Aimee Teegarden), it’s a battle of wills as she finds herself drawn to the guy (Thomas McDonell) who gets in the way of her perfect prom.