If you take the GRE or TOEFL more than one time and send the official test scores to GSAS, we will forward all of your test scores to the department. Departments usually look at all of the test scores they receive on your behalf. Admission committees may use the most recent test score, the highest test score, or some combination of the scores. This is at their discretion; there is no standard policy set by the Graduate School.
在该校MA和PhD的FAQ里又有:
Q: If I take the GRE multiple times, how do you combine them?