ACT officials say a more diverse test-taking population and a weakened high school curriculum are partly responsible for this year's less-than-stellar results, The Wall Street Journal reported Wednesday.
About 47 percent of 2010 high school graduates, or 1.6 million students, sat for the ACT exam, which measures mastery of high school curriculum on a scale of 1 to 36.
This year, the average composite score was 21, down 1/10th of a point from last year.
About 70 percent of 2010 test-takers reported taking a core curriculum in high school that consisted of four years of English and three years each of math, science and social studies.
Cynthia Schmeiser, who heads ACT's education division, said the results suggest core courses offered in high schools are not sufficient to prepare students for college.