A mistake in the scoring of the principal university admissions exam has thrown the whole process into chaos only days before US high school students were to learn whether they had been admitted to the university of their choice.
The College Board, the organisation that administers the SATs, acknowledged that 4,000 of this year's papers were scored inaccurately - a tiny fraction of the total number of tests taken.
The board said that the remainder of the 491,000 tests taken that day were marked accurately. Almost immediately, however, 1,600 more incorrect scores showed up.
The culprit was rain in the northeastern US on the October day the test was given, which increased the moisture content in the answer sheets, causing the paper to expand and throwing off the scanners that grade the multiple-choice sections.
The mistakes lowered the resulting SAT scores for most of the affected students, in some cases by as much as 400 points out of a possible total of 2,400. For a lucky few, scores were as much as 600 points higher than deserved.
With the announcement by the College Board coming not long before the April 1 date on which universities notify students whether they have been accepted, the debacle could accelerate a continuing move away from relying on test scores in admissions, said Robert Schaeffer, spokesman for the National Centre for Fair and Open Testing. Some 730 four-year American universities, or about a third of the total, no longer require applicants to submit test scores, and the number has been growing.
"This comes at the worst possible time in terms of exhaustion in the college admissions world," Mr Schaeffer said.
The SAT scoring errors meant that admissions departments "had to go back and wade through tens of thousands of decision envelopes to pull the ones they had to review," he said.
"Before this scoring fiasco, we knew of at least a dozen more universities that were re-examining their test-score requirement. They will be re-examining it now with more intensity and anger," Mr Schaeffer said.
The US Department of Education plans to investigate test-scoring mistakes on the SAT and on other standardised tests given at various grade levels.
Some lawyers have suggested that students whose tests were graded incorrectly may have a legal claim against the College Board.
The College Board said it had not been notified of any legal action. It said that, in future, it would allow test papers to dry out in a warehouse in Texas before feeding them through the scanning machines.
"We very much regret any further worry or inconvenience that this problem may have caused students and families," the organisation said.