“Cinderella never had it this bad,” begin the press notes for this banal teen romance starring Hilary Duff and Chad Michael Murray. Actually, Cinderella never had it this good: Duff’s trials consist of working part-time at a retro 50s diner in North Hollywood, waiting on an admissions letter from Princeton, and driving her late father’s classic Mustang to school instead of a new car. Having defused the fairy tale, first-time screenwriter Leigh Dunlap pads this out to 96 minutes with stale high school politics and the usual claptrap about believing in yourself. Mark Rosman directed; with Jennifer Coolidge as the evil stepmother and Regina King as the fairy godmother, a mildly sassy waitress. PG, 97 min.