George Washington University reported 78 percent of incoming freshman in the class of 2015 graduated in the top 10 percent of their high school class, but it's actually 58 percent.
President Steven Knapp says the university wasn't intentionally overstating the numbers.
Since many high schools no longer rank their students by percentile, the admissions office guessed where accepted students fell in their class based on GPA and standardized test scores.
University officials say they've been using this methodology for over 10 years, and that the problem was discovered during an administrative reorganization.
In September, U.S. News & World report ranked the university 51st in the nation. The academic credentials of incoming freshman is a variable used for this and several other rankings.