Najima and Nayaba Bawa were despondent when their parents first raised the subject of sending them home to Ghana. It was three years ago, one evening as their mother was braiding Nayaba's hair. Najima, then in junior high, had lost focus in school. Hanging out with friends had become more important than studying. She had even brought home a few C's on her report card. They had reached a decision, the girls' parents calmly informed them. They were sending them to the Akosombo International School, a boarding school in the eastern Ghananian town of Akosombo, about 80 kilometers, or 50...