Actually. Research shows that the two together (SAT and GPA) are the best predictor. “Validity studies have consistently found that high school grades and SAT scores together are substantial and significant predictors of achievement in college. In these studies, although high school grades are typically slightly better predictors of achievement, SAT scores add significantly to the prediction.” And of the SAT, the writing portion has the highest capability of predicting college GPA. (“Validity of the SAT for Predicting First-Year College Grade Point Average” Jennifer L. Kobrin, Brian F. Patterson, Emily J. Shaw, Krista D. Mattern, Sandra M. Barbut; “The SATand High School Grades: Utility in Predicting Success in College” Camara, Wayne J.; Echternacht, Gary)