SAT reading scores for the high school class of 2011 were the lowest on record, and combined reading and math scores fell to their lowest point since 1995.

The College Board, which released the scores Wednesday, said the results reflect the record size and diversity of the pool of test-takers. As more students aim for college and take the exam, it tends to drag down average scores.

Meanwhile, other tests taken by more representative groups of high school students have shown reading skills holding steadier. And in the context of the 800-point test, the three-point decline in reading scores to 497 may seem little more than a blip.

Still, it’s just the second time in the last two decades reading scores have fallen as much in a single year. And reading scores are now notably lower than as recently as 2005, when the average was 508.

Average math scores for the class of 2011 fell one point to 514 and scores on the critical reading section fell two points to 489.

College Board officials pointed to a range of indicators that the test-taking pool has expanded, particularly among Hispanics, which is a good sign that more students are aspiring to college. For instance, roughly 27 percent of the 1.65 million test-takers last year came from a home where English was not the only language, up from 19 percent just a decade ago.

But the increasingly diverse group of test-takers is clearly having more trouble with reading and writing than with math. Wayne Camara, College Board vice president of research, said recent curriculum reforms that pushed math instruction may be coming at the expense of reading and writing — especially in an era when students are reading less and less at home.

“We’re looking and wondering if (more) efforts in English and reading and writing would benefit” students, Camara said.

Gary Phillips, chief scientist at the American Institutes of Research, cautioned against using SAT scores as a way to measure national performance.

Overall on reading, “I think we’re treading water in the long-run,” Phillips said, citing other tests like the National Assessment of Educational Progress. “In the short run, we’ve had a few blips in a couple directions. Based on the international comparisons, however, we’re still not doing all that well.”

Bob Schaeffer, public education director of the group Fair Test, a longtime critic of the SAT, found unpersuasive the College Board’s explanation that the declines were due largely to a broadening test pool. In 2003, he said, the number of SAT-takers expanded by a greater percentage than last year, but scores that year rose 6 points on math and reading.

“Yes, changing test-taker demographics matter,” he said. “No, they don’t explain a 18-point drop (in combined scores) over five years.”