Gift of the Unmage, book 1 in the Worldweavers series by Alma Alexander.
Double Seventh, the seventh child of two parents who were also seventh children. Amazing magical ability. As the world watches, Galathea Georgiana Winthrop fails every assignment, every exam, and every teacher that tries to find out her magical gifts. As a last resort her father sends Thea back in time to a Anasazi elder who doesn't exactly teach but simply walks...
When Thea returns with still no signs of her magic, she is sent to the Wandless Academy, a school for the magically inept.
There in a place of no magic Thea faces the battle of her life.
Check out Gift of the Unmage by Alma Alexander at your local library or on amazon.com
Ages 12 and up. If you like Harry Potter or Diana Wynne Jones Young Wizard series you will enjoy this book.