This study explores the educational achievement of immigrant youth in Spain employing data from 3 waves of the Longitudinal Study of Families and Childhood (Panel de Families i Infancia), a representative sample of children in Catalonia first interviewed at ages 13-16 in 2006 (N = 2,710). Results suggest consistent disadvantage in achievement among first-generation students. Differences in achievement between the second and third generations are apparent in bivariate analyses, but are explained by observable characteristics in multivariate analyses. Gender-specific analyses uncover a large achievement gap between first-generation girls and their third-generation counterparts, but no equivalent gap for boys. Region-of-origin differences are modest, with the exception of Latin American adolescents who exhibit the lowest educational outcomes. The significance of perceptions about school on achievement are discussed. (Contains 5 tables.)