Funny thing is that I recently saw a "prom dress" magazine at the doctors office. I flipped through it because my daughter will be buying one in a couple of years (after we get through the sweet sixteen dresses! -- I told her to start saving). Anyway, what stood out was that some of the models were obviously in their 20s (later 20s even), and then some of the dresses were a bit on the skimpy side. I don't mean too much cleavage in a prudish manner, I mean little more than two straps running from shoulder to waist.
Then there was the junior high school prom (when I taught junior hs) that was summed up by a female teacher as "the girls looked stunning in their lovely gowns. then the music started and they all started dancing like tramps and hookers."