Claremont McKenna College, a small, prestigious California school, said Monday that for the past six years, it has submitted false SAT scores to publications like U.S. News & World Report that use the data in widely followed college rankings. In a message e-mailed to college staff members and students, Claremont McKenna’s president since 1999, Pamela B. Gann, wrote that “a senior administrator” had taken sole responsibility for falsifying the scores, admitted doing so since 2005, and resigned his post. People briefed on the matter said that the administrator was Richard C. Vos, vice president and dean of admissions, whose name was removed in the last few days from the college’s online list of top officials. Mr. Vos, reached at his home Monday night, said: “No comment. It’s an internal personnel matter.” The critical reading and math scores reported to U.S. News and others “were generally inflated by an average of 10-20 points each,” Ms. Gann wrote. For the class that entered the school in September 2010 — the most recent set of figures made public —the combined median score of 1,400 was reported as 1,410, she said, while the 75th percentile score of 1,480 was reported as 1,510. Such small differences might influence the rankings, and the deception underscores the importance those rankings have taken on, as colleges fret over the loss of even a notch or two against their competitors. Robert Franek, the senior vice president of publishing for The Princeton Review, which provides preparation for the SAT and also ranks colleges, said that he had never heard of a college intentionally reporting incorrect data. “We want to put out very clear information so that students can make an informed decision about their school,” Mr. Franek said. “I feel like so many schools have a very clear obligation to college-bound students to report this information honestly.” The Princeton Review bases its college rankings on student opinion rather than test data, Mr. Franek said, so he was uncertain whether a change as small as that reported would make a difference. “It’s hard for me to say, but that is a small percentage,” Mr. Franek said. “That is a pretty mild difference in a point score. That said, 10 points, 30 points to a student that isn’t getting that score on the SAT could be an important distinction.” Claremont McKenna, a liberal arts school with about 1,200 students and a strong focus on political science and economics, is part of the Claremont colleges cluster east of Los Angeles. Long considered a good school, in the last generation it has moved into the elite ranks — at least as measured by the most-popular ratings. The current U.S. News rankings list Claremont McKenna as the ninth-best liberal arts college in the country, a fact noted on Ms. Gann’s biography on the college’s Web site. The Princeton Review gives the college an academic rating of 97 out of 99 and an admissions selectivity rating of 96 out of 99, comparable to some Ivy League schools. It remains to be seen whether the revelation of falsified test scores changes that status. Ms. Gann wrote in her message that she was first warned of inaccurate reporting this month and asked other administrators to investigate, leading to an administrator’s admission of guilt and Monday’s announcement. “At this time, we have no reason to believe that other individuals were involved,” she wrote. “As an institution of higher education with a deep and consistent commitment to the integrity of all our academic activities, and particularly our reporting of institutional data, we take this situation very seriously.” She added that the college has alerted the publishers of college rankings and has hired the law firm O’Melveny & Myers to investigate further. A version of this article appeared in print on January 31, 2012, on page A12 of the New York edition with the headline: College Says It Exaggerated SAT Figures For Ratings.