Chrissa (american girl: girl of the year 2009, book 1)

Chrissa Maxwell moves to a new school in the middle of the year, and the girls in her fourth-grade class are decidedly unfriendly. On the advice of her grandmother, Chrissa tries first to be nice, and then to ignore the mean girls. But they just won't quit, and when the teasing turns into serious bullying, Chrissa must find the courage to stand strong and speak out.