Scores among every racial group except for those of Asian descent declined from 2006 levels. A majority of test takers - 57 percent - did not score high enough to indicate likely success in college, according to the College Board, the organization that administers the test.
The national trend lines are alarming and should serve as "a call to action," College Board president Gaston Caperton said. "When less than half of kids who want to go to college are prepared to do so, that system is failing."
The nearly four-hour SAT covers critical reading, writing and math. Each subject is worth a maximum of 800 points, for a potential total of 2400 points. For generations, SAT scores have been used, in conjunction with grade-point averages, by college admission officers to judge whether an applicant is likely to succeed at their school.
But questions about whether the SAT is biased in favor of middle-class and wealthy students have led many colleges to use other gauges or to accept an alternative exam, the ACT, which edged out the SAT in 2012 for the first time as the most popular college entrance exam.
There is a significant correlation between family income and test scores on the SAT, with average scores increasing with every $20,000 in additional family income.
Educational experts are divided over the causes. Some assert that privileged students do better on the SAT because they are exposed to activities, from summer camp to private violin lessons, that give them an advantage in that particular test. Others point to the fact that affluent parents can provide private tutoring and privileged students can afford to take the test multiple times.
Still, many school districts - and parents - traditionally have seen SAT scores as an important measure of the quality of a K-12 education.
Across the country, 1.66 million seniors who graduated in June took the SAT, the highest number since the exam was first administered in 1926 to a few thousand privileged students headed for Ivy League schools. In many places, school administrators have been nudging more students to take the exam, saying that all students should consider college.
The average reading score for the 2012 graduating class was 496, down 1 point from the previous year and 34 points since 1972. The average score on the writing portion of the exam was 488, down 9 points since that subject was first tested in 2006. Math scores were flat, compared with 2011.