Average math and reading SAT scores fell four points for the high school class of 2007 to their lowest mark since 1999, according to a report released Tuesday by the College Board.

Last spring's graduating seniors scored on average 502, out of a possible 800 points, on the critical reading section of the country's most popular college entrance exam, down from 503 for the class of 2006. Math scores fell three points from 518 to 515.

Click here to read a state-by-state breakdown of 2007 SAT results.

Click here to read a state-by state breakdown of 2006 SAT results.

This year's declines follow a seven-point drop last year for the first class to take a lengthened and redesigned SAT, which included higher-level math questions and eliminated analogies. The College Board, which owns the exam, insisted the new exam wasn't harder and attributed last year's drop to fewer students taking the exam a second time. Students typically fare about 30 points better when they take the exam again.

The College Board's score report, for release Tuesday, did not offer an explanation why this year's scores were even lower, but it did note that a record number of students — just short of 1.5 million — took the test. The cohort of test-takers also was the most diverse ever, with minority students accounting for 39 percent: There has been a persistent gap between the scores of whites and the two largest U.S. minority groups, Hispanics and blacks.

In New York, 99 percent of students took the exam, up from 88 percent last year. Maine recently became the first state to use the SAT to meet its Grade 11 assessment requirements under the federal No Child Left Behind Act, and 100 percent of students took the exam there, compared to about three-quarters in the class of 2006.

While the growing number of test-takers is considered a sign more people are interested in college, it can also weigh down average scores, because the pool of test-takers expands by including, on average, more lower-scoring students.

The number of black students taking the SAT rose 6 percent, and the number of test-takers calling themselves "Other Hispanic, Latino or Latin American" (a group that does not include Puerto Ricans or Mexican Americans) rose more than 25 percent.

Average scores also slipped from 497 to 494 on the writing portion of the SAT, which debuted with the class of 2006. Many colleges are waiting to see results from the first few years of data on the writing exam before determining how to use it.

Figures released earlier this month on the rival ACT exam showed a slight increase — from 21.1 last year to 21.2, on a scale of 1 to 36 — for the class of 2007.

The SAT has historically been more popular on the East and West coasts, while the ACT has been more popular in the Midwest and inland western states. But more and more students are taking both exams to try to improve their college resumes.