Seventh-grader Sierra Shepard has always been the perfect student, so when she sees that she accidentally brought her mother's lunch bag to school, including a paring knife, she immediately turns in the knife at the school office. Much to her surprise, her beloved principal places her in in-school suspension and sets a hearing for her expulsion, citing the school's ironclad no-weapons policy. While there, Sierra spends time with Luke, a boy who's known as a troublemaker, and discovers that he's not the person she assumed he would be-and that the lines between good and bad aren't as clear as she once thought.