Starting in Great Britain, Isabelle "Izzy" and Annabelle "Annie" Woods are introduced as clever twin girls with a love for pink like their cousin, Elle. They and their widowed father are moving to Southern California where they will be staying in Elle's home. Awaiting the girls are a pair of chihuahua dogs, their giddiness is cut short when they find out they are going to attend Pacific Preparatory, a private school requiring uniforms.
Upon their first day, Izzy and Annie are registering themselves and they sign for ID cards. They also start off on the wrong foot with Tiffany Donohugh (Brittany Curran), the spoiled daughter of a primary funder of "Pac Prep." And they also meet Chris, who is almost immediately smitten with Annie.
Tiffany later apologizes for her rude behavior and befriends the twins, although she is doing it merely to "keep her enemies close." Annie and Izzy believe Tiffany to be a sweet person, though she dislikes classmates on scholarship. However, her true colors come out, when she embarrasses Annie and Izzy at a formal dance, revealing that they are on partial scholarship at the school.
Izzy and Annie rekindle their friendships with the other scholarship students, including Chris. Izzy wants to help Chris get closer to Annie, but in several instances, Annie believes Chris to like Izzy. The twins and their friends believe the uniforms are stifling their creativity and they redo their clothing while still cleverly abiding by the school's many rules.
Chris and Izzy are later accused of cheating on a big history test and they all set out to prove the school wrong. Izzy and Annie suspect Tiffany and Justin are behind this and find that Chris and Tiffany have the same backpack that comes with a lock and key. In Chris's locked zipper he keeps a master-key, that opens all doors in the school, for his work-studies to help pay off his scholarship. They discover that all the keys and locks for the backpacks are the same, any key will open any lock. On the floor of the teacher's private office, where the answer key is kept, they discover red markings that match the marks that Justin's expensive shoes create. Tiffany told Justin the uber code to access the answers to the test.
With this new piece of information, Annie and Izzy set to prove Izzy's innocence. In student court, Annie poses as Izzy when she is locked in the bathroom by Justin, and defeats her fear of public speaking. Even as Izzy escapes and returns to the court, Annie points out that Justin owns a new cell phone, one that has not yet been released to the public, and could only have gotten from one person, the daughter of the creator, Tiffany Donohugh.
Annie wrote down the uber code and analyzed it with the markings and studied them in court and told everybody that Justin is so expelled because only the creator can tell the person that is doing it. Justin, who is irritated by noises such as pencils being sharpened and pen clicks, struggles to hold himself together as the entire courtroom click their pens. He finally admits to framing Chris and Izzy and that Tiffany was in on it too. Headmistress Higgins expels them both.
Annie and Chris dance together at a school dance and Izzy does the same with Brad who is also a scholar but kept it a secret, he had aided them in proving Justin's guilt. Tiffany and Justin are shown boarding a yellow school bus at a public school, Tiffany's worst fear came true. However, as the couples joyously dance, Ashley Meadows, Tiffany's former sidekick, icily warns them from afar,"It's not over girls. There's a new brunette in charge!"