The Chysalids: John Wyndham

A Sci-fi book from 1955 about a post apocalypic world, apparently after there was radiation as they "cull" both animals and humans that don't fit the decription of perfect humans. David, whose father is the minister, has the power of telecommunication along with 5 other children in town. His uncle and mother tell him to keep the ability to himself, whough he is too young to really understand why. His friend Sofie has 6 toes which her parents have kept hidden until she hoes swimming and someone spots her 6 toed wet footprint on a rock. Her family smuggles her out of town. David then has a little sister born who has his telepathic abilities only stronger. He escapes with her and his cousin to start a new life thinking there are more people like them. They meet up with Sofie who is living in a cave...and you don't really know what becomes of them.