Um, the "pre-teen" you are speaking about is a 22 year old adult. As I have said in previous postings, Miss Spears probably does dress a bit too provocatively. But, let's put it in proper context for a bit. When she is dressed so provocatively, she is performing on stage. Is she any less covered than the average Radio City Rockette was in the 1940's? Besides, nothing she has worn in public (that I have seen at least) would be considered more than PG-13, and probably could make it into a PG movie too!
Nice try (Not work-safe). Britney was bursting out of a Catholic schoolgirl uniform (with blouse tied like a halter and her navel showing) in her first video for "Baby One More Time," and things have progressed -- or regressed -- from that point. The Rockettes, famed for their long and luscious legs, didn't have outfits that showed cleavage until 1982.
Besides, nothing she has worn in public (that I have seen at least) would be considered more than PG-13, and probably could make it into a PG movie too!
Again, I say, nice try (not work-safe either).
That speaks more to what is allowed in a PG-13 movie nowadays. Ten years ago, there's no way that, for example, Van Helsing would have gotten PG-13. Bruce Almighty probably wouldn't have either, with it's F-word in a key scene.
Besides, the conventions are not for immature teenagers going to the movies, they are for voting-age adults.