While prior research has explored the neurobiological mechanisms underlying adolescent school performance, these mechanisms remain poorly understood in college students. Impulsivity has been highlighted as a key factor affecting academic success; however, its influence on the relationship between school performance and brain structure remains underexplored. In this study, we used a sample of college students to investigate which gray matter volume (GMV) in brain regions was associated with grade point average (GPA), and whether impulsivity mediates these relationships. Our findings revealed correlations between GMV in the caudate nucleus (CN) and cerebellum with GPA. Increased CN was correlated with poorer GPA through higher impulsivity, whereas higher cerebellum was associated with better GPA through lower impulsivity. These results indicate that CN and cerebellum play crucial roles in school performance and associated impulsivity. Various interventions targeting impulsivity, such as therapy, counseling, and medication, could improve educational outcomes by addressing the underlying neurobiological factors.