Harmony by Carolyn Parkhurst
How far will a mother go to save her family? The Hammond family is living in DC, where everything seems to be going just fine, until it becomes clear that the oldest daughter, Tilly, is developing abnormally--a mix of off-the-charts genius and social incompetence. Once Tilly--whose condition is deemed undiagnosable--is kicked out of the last school in the area, her mother Alexandra is out of ideas.
The family turns to Camp Harmony and the wisdom of child behavior guru Scott Bean for a solution. But what they discover in the woods of New Hampshire will push them to the very limit. Told from the alternating perspectives of both Alexandra and her younger daughter Iris (the book's Nick Carraway), this is a unputdownable story about the strength of love, the bonds of family, and how you survive the unthinkable.