Stargirl by Jerry Spinelli (2002, Trade Paperback)

Leo Borlock follows the unspoken rule at Mica Area High School: don't stand out—under any circumstances! Then Stargirl arrives at Mica High and everything changes—for Leo and for the entire school. After 15 years of home schooling, Stargirl bursts into tenth grade in an explosion of color and a clatter of ukulele music, enchanting the Mica student body. But the delicate scales of popularity suddenly shift, and Stargirl is shunned for everything that makes her different. Somewhere in the midst of Stargirl's arrival and rise and fall, normal Leo Borlock has tumbled into love with her. In a celebration of nonconformity, Jerry Spinelli weaves a tense, emotional tale about the fleeting, cruel nature of popularity—and the thrill and inspiration of first love.