This paper reports on research to examine the types of motivation related to school achievement. A total of 1428 students from an inner city high school in the Montreal (Quebec) area participated in the study, 714 males and 714 females. The students ranged in age from 12 to 18, and approximately 40 percent were minorities (Hispanic, Asian, Black). The study used the "Academic Motivation Scale" (AMS), a measure of motivation toward education based on self-determination theory. "Amotivation" indicates that no link between actions and the ensuing outcomes is perceived; "intrinsic motivation" refers to being engaged in an activity for itself and for the pleasure and satisfaction derived from participation; "extrinsic motivation" pertains to behavior in which the goals of actions extend beyond those inherent to the activity itself. The results of the study demonstrated that academic motivation is significantly related to grade point average (GPA), and that motivation does not occur under the same conditions for boys and girls or for junior-high and senior-high students. Amotivation appeared to be a better predictor of school achievement for girls and junior-high students, while intrinsic motivation seemed to foretell school achievement for boys and senior high students. These data revealed that the relationship between GPA and motivation emerged differently for boys and girls, as for younger and older students. The data also indicated that amotivation was the type of motivation most significantly related to GPA for both boys and girls, across all levels of secondary schooling. The findings suggested that development of self-determined motivation in adolescent boys and girls should be an important goal for educators, and that further study of amotivation could lead to better understanding of adolescent academic motivation and perhaps help to identify at-risk students. (Contains 31 references.) (ND)