Four thousand high school students who took the SAT in October received low scores on the test incorrectly because of a problem with scanning machines, the company that administers the test said Wednesday.
The College Board has now contacted the students, a few of whom received scores that were lowered by as much as 400 points. The test is scored out of 2,400.
The students, who represent only 0.8 percent of those who took the test, will receive a refund for the testing fees, and the schools to which they applied have been notified.
Jennifer Topiel, a spokeswoman for the College Board, said the company was confident that the error was a "onetime-only thing."
There were 894 students from New Jersey who received incorrectly-graded tests, Topiel said, but she declined to disclose how many applicants to the Princeton Class of 2010 may have been affected.
Topiel said that the University admission office had the information, but Dean of Admission Janet Rapelye was unavailable for comment.
"To have it come this late is really challenging," Penn admissions dean Lee Stetson told The New York Times on Thursday. "We've been through half the admitted class already, and now we have to stop everything and review those students who were affected."
Robert Hill, director of college advising at St. Paul's School in Concord, N.H., said that students who received word that their scores were inaccurately low should contact the colleges they applied to as soon as possible, adding, however, that the scoring snafu is probably more trouble for the SAT's image than for the affected students.
Hill said that the hype surrounding the new SAT — now four and a half hours long with a writing section — has been a "PR nightmare" for the College Board since its debut in March 2005. "With this [scoring] problem, all that stress has been actualized," he said.
But Hill also said that the problem, if unnoticed, could easily have been a determining factor in college admissions. "A 200-point difference at the most selective colleges can change the decision readily," he said.
Though the problem was first reported Wednesday by the Times, the article noted that the College Board has been aware of the problem since late December.
Kim Williams, an official at The Princeton Review, a test prep company unaffiliated with the University, speculated that the College Board decided that the problem was a proportionally minor one and could be dealt with on a "low-key level."

"This not being as forthright about it as they could have been lends a little more credibility to people who say the SAT is not ethical," Williams said.