This paper presents an in-depth cross-case analysis of three high-achieving young adolescent girls who had contrasting mathematics learning experiences during the first year of middle school. In particular, this study examines the foundation for their motivation, as well as the dominant mode of learning and academic engagement in relation to three sociocultural factors, family background, the role of peers, and the level of teachers' understanding of the students and instructional support provided. Our data analysis revealed that the three girls possessed motivation structures and learning dispositions that are more or less prone to conceptual or procedural understanding in mathematics. This resulted in a significant variation in the mode of their academic engagement with the subject, and this provided a different set of challenges in each girl's pursuit of higher level of mathematics learning.