One Crazy Summer by Rita Williams-Garcia

Eleven-year-old Delphine hopes to find out the answers to why her mother left her and her two sisters, Vonetta and Fern, when the youngest, Fern, was just a baby.  They haven't had any contact with their mother, Cecile, but their father decides that they are old enough to spend a month with her and sends them on their way, despite her grandmother's, Big Ma's wishes.  However, instead of a warm reception, they find their mother is cold and distant, takes their money, refuses to call Fern by her name, and won't let them in the kitchen for any reason.  Instead of feeding them, she sends them out for take-out and sends them to a summer day camp run by the Black Panthers to keep them out of her hair.  Will Delphine find the answers she is desperately looking for?  How can she keep her sisters safe when the Black Panthers are being watched by the police?