You can create your own custom predictors and supply data for them, or select predictors from the ACES system that ACES has data for, collected from the SAT Questionnaire (which SAT takers opt in to) or AP Exam data. These include average AP Exam score (calculated prior to senior year of high school), number of different AP Exams taken, number of honors or AP courses taken during high school, and number of activities during high school.
The primary purpose of an admission validity study is to evaluate the measures that are used in admission decisions—the predictors—to determine how well they work alone and in combination to predict student success. A good predictor, however, has several other important qualities. It should be widely available, reliable, and fair to all students. Predictors should show sufficient variation in scores to differentiate student ability, without large clumps of students at the top or the bottom scores.
When selecting predictors to include in your study, you should consider including any possible contributors to your admission decisions. ACES can help to sort through them for redundant or weak contributors, as well as providing prediction equations for future students.
The ideal prediction equation has multiple predictors that measure relatively different characteristics, and consequently, are not highly correlated with each other. In such a situation, the correlations between the individual predictors and the criterion are more or less "additive." A less-than-ideal situation occurs when the individual predictors measure similar constructs, and consequently, are highly correlated (e.g., high school rank and high school GPA); the worst case is when two predictors are perfectly correlated.