This study explored how the SAT and High School Grade Point Average (HSGPA) can work together to help institutions to confidently admit, place, and support students in their academic majors while promoting student opportunity and success as well as institutional health and success. In particular, this study examined the differential validity of the SAT for predicting second-year cumulative grade point average (SYCGPA) and students' chances of earning a SYCGPA of 3.0 or higher across 13 academic majors, with a special emphasis on STEM majors and STEM students who come from educationally disadvantaged environments. This information can be helpful for campus initiatives focused on major choice, academic success within major (as measured by grades), and retention within major. Subgroup analyses found that STEM students who came from educationally disadvantaged environments had lower probabilities of earning a SYGPA of 3.0 or higher even when they had the same SAT scores and HSGPAs of their peers, suggesting that these students may benefit from increased institutional support as colleges and universities seek to diversify the student body in the STEM fields. Paying attention to both SAT scores and environmental context information can help institutions to target instructional supports to the students that need them most to ensure that all students have the opportunity to be successful in their chosen major and have additional opportunities later on for graduate school and recruitment by top employers, that may in part be selected by cumulative GPA.