Using longitudinal data from the 4-H Study of Positive Youth Development, the authors assessed 1,977 adolescents across Grades 5 to 8 to determine if there were distinctive developmental paths for behavioral and emotional school engagement; if these paths varied in relation to sex, race/ethnicity, and family socioeconomic status (SES); and whether links existed between trajectories of school engagement and grades, depression, substance use, and delinquency. Four trajectories for behavioral school engagement and four trajectories of emotional engagement were identified using a semiparametric mixture model. These trajectories were distinct with regard to initial levels of and changes in engagement, as well as to their shapes. Trajectories varied in regard to sex, SES, and race/ethnicity. Different trajectories of behavioral and emotional engagement were linked to grades, depression, delinquency, and substance use. Directions for future research and application are discussed. (Contains 3 footnotes, 6 tables, and 2 figures.)