Sorority Girl by Anne Emery
It is a big moment in Jean Burrnaby's life when she is asked to join her high school sorority, the Nightingales. For a while sorority life is a dream come true, but Jean discovers joining a sorority isn't quite what she thought it would be. Jean sees both sides of sororities: the heartbreak of being left out and the disillusionment of being "in." She, ultimately, makes a decision that astonishes Sherwood High.