In theory, other measures of student achievement: grades, extracurricular activities, personal statements, letters of recommendation. GPA by itself isn't terrible for this, though pairing it with test scores is an improvement over both it by itself and test scores by themselves for prediction of academic success in college.
In practice: things that satisfy ideological goals and maximize fundraising outlook for the institution.
In practice: things that satisfy ideological goals and maximize fundraising outlook for the institution.