The number of high–school graduates who took the ACT and met all four of its college-readiness benchmarks has risen for the third year in a row, with the ACT also testing its largest class ever this year.

Twenty-five percent of the class of 2011 met the ACT College Readiness Benchmarks in math, science, English, and reading. The benchmarks are the ACT‘s measurement of the likelihood a student will earn a C or higher in a typical first-year college course in that subject.

The gains, though, were marginal: 24 percent of all class of 2010 test-takers met the four benchmarks last year. The average composite score was nearly the same this year as it was last year, up from 21.0 to 21.1.

“There is still a significant range of students in there this year, with a quarter of them not meeting any benchmarks,” said Jon L. Erickson, interim president of the ACT‘s Education Division. For those who consider the benchmarks to be an evaluation only of students who have self-selected themselves as collegebound, Mr. Erickson said, “that should be some cause for alarm.”

But not all the test takers plan to attend college, he pointed out, as more states have started to test all of their high school students with the ACT, making the test an increasingly accurate barometer of trends in higher-education preparedness among all high school students.

More than 1.62 million graduating seniors took this year’s test, or 49 percent of the class of 2011. The highest proportion ever, 26 percent, were African-American or Hispanic/Latino. Robert A. Schaeffer, public-education director for the National Center for Fair & Open Testing, says those numbers are consistent with overall demographic trends in the U.S. collegebound high–school population.

The racial-achievement gaps reported last year have persisted among this year’s graduating class, however. The average score was 17 for black students, 18.7 for Hispanic/Latino students, and 22.4 for white students, each up only 0.1 point from last year. Asian students‘ average composite score was 23.6, up from 23.4 last year, and American Indians/Alaska Natives’ average score fell, by nearly half a point, to 18.6. Native Hawaiian/Pacific Islander students‘ average score this year was 19.5, and was not measured last year.

The percentages of students meeting benchmarks vary widely among races, too. Forty-one percent of Asian students and 31 percent of white students had the minimum scores for college readiness in all four areas, compared with 15 percent of Native Hawaiians/Pacific Islanders, 11 percent of American Indians/Alaska Natives, 11 percent of Hispanic/Latino students, and 4 percent of black students.

Taking the long view, Mr. Erickson says that over a period of about five years, the ACT has found encouraging trends in mathematics and science, even though a low proportion of students meet the college-readiness benchmarks in those areas-45 percent and 30 percent this year, respectively, up from 43 percent and 29 percent last year.

“We’re seeing a positive gradual improvement,” he says. “But gradual isn’t strong enough.”

But across the board, he says, students‘ reading and writing skills have failed to improve. Fifty-two percent of test-takers passed the college-readiness benchmarks for reading this year, and 66 percent passed the benchmarks for English, the same proportions as achieved by the class of 2010.

“Reading in many places falls off the map when students get to high school,” Mr. Erickson says. “Nobody owns reading.”

Mr. Schaeffer cautions against using the test as a measure of college readiness, as the ACT‘s measurements have never been independently evaluated. But they provide a consistent measurement of how graduating high–school classes compare from year to year, he says, and he agrees that the outlook is worrisome.

“Reading is one of the major things that was the focus of No Child Left Behind,” says Mr. Schaeffer. “If you graduated in 2011, you experienced No Child Left Behind for nearly all of your education, from fourth grade onward. Yet this shows there has been very little progress made. No Child Left Behind has been a failure by measure of these tests. “