In the United States a prom , short for promenade , is a semi-formal (black tie) dance held at the end of an academic year, in high school senior and junior students (last two years) attending this event. Boys usually dress in black tie (a dinner jacket and bow tie ) and girls traditionally wear formal gowns or dresses . The style of these prom dresses has changed over the decades. Most recently large ball gowns, slinky dresses and short length dresses have proved popular. Ana enjoyed participating in her school prom dance and activity