The findings sound contradictory. But the exam's authors point to a growing and more diverse group of test-takers - many are likely scoring lower overall, but more are also meeting benchmarks used to measure college readiness.
Last spring's high-school seniors averaged a composite score of 21.0 on the test's scale of 1 to 36, down slightly from 21.1 last year and the lowest score of the last five years.
At the same time, 24 percent of ACT-tested students met or surpassed all four of the test's benchmarks measuring their preparedness for college English, reading, math and science. That is up from 23 percent last year and 21 percent in 2006.
Although that still shows three in four test-takers will likely need remedial help in at least one subject to succeed in college, ACT officials are encouraged to see improvement as ever-larger numbers of students take the exam.
"It's slow progress," said Cynthia Schmeiser, president and chief operating officer of ACT's education division. "We are headed in the right direction."
Schmeiser highlighted slight gains in math and science readiness, traditional weak spots for U.S. students. The number of students prepared for college-level biology, for example, has risen from 21 percent to 24 percent in five years.
On the not-so-encouraging front, ACT-takers prepared for college English have dropped from 69 percent to 66 percent in that span. Still, English remains a strong suit for ACT test-takers compared to other subjects.
To measure whether students are ready for college, the ACT sets minimum scores in a subject area test to indicate a 50 percent chance of getting a B or higher or about a 75 chance of getting a C or higher in a first-year college credit course. The courses include English composition, algebra, biology and introductory social science courses like Psychology 101.
The ACT report found a combined total of 43 percent of test-takers met either none or only one of the four college readiness benchmarks.
A record 1.57 million students, or 47 percent of this year's high school graduates, took the ACT. That's a 30 percent increase from five years ago.
The SAT remains the most common college entrance exam, though the rival ACT has nearly caught up in popularity. Most colleges accept either, and a growing minority no longer requires either one. SAT results are due out Sept. 13.
Average SAT scoresfor the high school class of 2009, while gender, race and income gaps widened, according to results reported last year which broadly reflect the ACT new results.
The ACT is growing as more states require it for all high school seniors, meaning test-takers are not just the college-bound.
Schmeiser noted that the ACT's test-taking population "now includes virtually all students in eight states, many of whom might not have considered taking a college and career readiness assessment years ago." The ACT says another three states - Arkansas, Texas and Utah - either have been or soon will make state-financed ACTs available to all districts.
One result: a more diverse pool. Ethnic and racial minorities this year made up 29 percent of all ACT test-takers, up from 23 percent in 2006. Most significant was a near doubling of Hispanic graduates tested, to almost 158,000 students.
The average composite scores for Hispanics dipped slightly to 18.6 this year after holding steady at 18.7 the previous three years.
Because some states mandate ACTS but others don't, state-to-state score comparisons can be misleading. States requiring all students to take the ACT typically see average scores go down, at least initially.