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.