The Summer of the Swans by Betsy Byars (Paperback)

A Newbery Medal Winner All summer Sara Godfrey has fretted over herself, her impossible body, her terrible new haircut. One moment she's elated, the next, she's in tears. And she can't figure out why. Maybe her wildly changing moods are tied to the sudden and unaccountable appearance of the swans, which hold the rapt attention of Charlie, Sara's mentally handicapped brother, who she loves far more than herself these days. In fact, it will be the sudden disappearance of Charlie that will compel Sara to abandon her own small, annoying miseries, and lose herself in searching for him. In her anguish, Sara turns to Joe Melby, whom she has long despised, and together they search through the dense woods and rough fields to find him. Sara knows that she will never be the same again.