Switched at birthday

Lavender sees herself as the miserable but tough outsider at school, while Scarlet knows she is talented and popular, but insecure on the inside--then, on their mutual thirteenth birthday, they wake up in each other's bodies and are forced to learn what it means to walk in someone else's shoes.

Lavender and Scarlet aren't friends. Lavender is something of an outcast, and Scarlet is amazingly popular. On their birthdays, they wake up in each other's bodies and have to figure out how to be someone who's completely opposite of who they are.