Bianca, a high school senior, giggles with her friends as they huddle around the full-length mirror, taking turns to admire their chosen prom gowns giddily. The 18-year-old is gushing over the black ...

For high schoolers across America, prom season means heady nights of corsages, limousines, broken curfews, and gaudy, bedazzled gowns—except, maybe not that last part anymore. The words prom dress ...