The purpose of this mixed-methods study was to explore the feasibility, acceptability, and preliminary effectiveness of a Tier 2 classroom-based motivational interviewing (MI) intervention--the Aspire Group Intervention (AGI)--designed for ninth-grade students identified as being at high risk for school dropout. The nine-lesson AGI curriculum was grounded in self-determination theory and positive youth development, and aligned with the four processes that characterize MI (i.e., engaging, focusing, evoking, and planning). The intervention was implemented with 38 ninth-grade students in two classrooms in one southeastern high school. Data were collected through pre/post student surveys, implementation fidelity checklists, and teacher interviews. Results suggest students were satisfied and found the intervention helpful. Teachers were satisfied with the intervention overall but shared concerns regarding student engagement and group size due to classroom delivery of the intervention. Implementation data suggest that lessons were slightly longer than a class period and most activities were implemented as intended. The article concludes with a discussion of implications of this study for future refinement of the intervention, along with more general implications for school social work practice.