Dannah Gresh & Janet Mylin 
Just Call Me Kate [EPUB ebook] 

Sixth-grader Kate Harding has bigger problems than trying to get her parents to stop call her Katie. She has a major crush on her older brother’s best friend: Zachary Donaldson. In a moment of insanity, she dares to write his name on the bathroom wall in eight-inch high pencil letters. It doesn’t take Principal Butter long to match the handwriting to the doodling on her book covers. Kate is sent to detention where she meets up with three new friends who decide to become the Secret Keeper Girl Club. Her case of boy craziness is doused with some good advice from her new friends.