National reading scores on the SAT college-entrance exam have sunk to their lowest point in 40 years, and the proportion of test takers deemed fully prepared for college remains flat at 43 percent, the test’s sponsors announced this morning.

The average score on the exam’s critical reading section among this year’s college-bound seniors dropped to 496 points, down one point from last year and 34 points from 1972. Each of the SAT’s three sections, critical reading, writing and mathematics, is scored on a range of 200 to 800.

Writing scores also dipped one point from last year, to 488, the lowest result since an essay-writing section was added to the test in 2006. The average writing score in that initial year was 497.

SAT math scores remained steady from last year, at an average 514 nationwide. That score, too, was down from a peak of 520, recorded in 2005.

The College Board calculated that 43 percent of SAT takers in this year’s freshman class were well-prepared for studies at four-year colleges. the same figure as in 2011. That’s based on the percentage of students scoring a combined 1550 points, an indication they would earn a B- average or better during their first year of college.