MC Not Going to Prom

OK, I read this article on Aol Red saying that Miley Cyrus wasn't going to prom, since she would be filming her movie then. I understand that she wouldn't care if she went since she doesn't have a date, all of the guys would be intimidated by her, and all the girls would be jealous of her. She would have a miserable time. But the thing I am wondering about is the fact that Miley is 15. She would be either a freshman or sophomore! So why would she be worrying about prom, when she isn't even old enough! Maybe she skipped a few grades? I would think that it would be common knowledge if she skipped grades, since the paparazzi have practically released every other detail about her life. Maybe her high school is weird, and has a special sophomore prom. But then why is there an article about her missing her prom, if she has two more years to go to a prom? This is a question that can be answered like a Tootsie Pop ad: the world may never know.