This study uses multilevel modeling to examine a subset of the highest performing 9th graders and explores the extent that achievement gaps in math widen for high performing African American and Latino students and their high performing White and Asian peers during high school. Using nationally representative data from the High School Longitudinal Study of 2009 (HSLS:09), this study aims to address three research questions: 1) To what degree does the achievement gap widen between different ethnic groups during high school; 2) To what extent can a widening achievement gap be explained by individual and school characteristics of students?; and 3) To what extent are the effects of various factors on achievement moderated by race/ethnicity? The study finds that factors such as advanced course placement and socio-economic status (both individual and school SES) explain away the gap for high achieving Latino 11th graders and some of the gap for African American 11th graders while student background explains away the large advantage for Asian 11th graders. Notably, the effect of math efficacy on math achievement is shown to vary by race/ethnicity. This study has important implications for post-secondary opportunities for high-achieving African American and Latino students.