Kentucky juniors scored an average of 18.3 on the ACT out of a possible 36, according to state results released Thursday.
The latest results include scores for all public school juniors for the first time. The state revamped rules to require the exams this year.
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The juniors who took the ACT in spring 2008 received an average composite score of 18.3.
The national average composite score in 2008 for all ACT-tested 2008 high school graduates (more than 1.4 million students) was 21.1, which was a decrease from 21.2 in 2007.
The average scores in Kentucky varied among races and slightly between genders.
Students described as American Indian/Alaska native received the lowest average composite score at 15.2, followed by African-American/black students with a score of 15.6.
Students in the Asian American/Pacific islander race group received the highest composite score: 20.1.
Males had an average score of 18.0, and females had 18.5.
A total of 42,929 Kentucky students took the test.
The exam, paid for by state funds, assesses English, reading, mathematics and science and was scored on a scale of 1 to 36.
In the individual subjects, which also were scored, 46 percent of the juniors met the English benchmark score, 20 percent met the mathematics benchmark, 33 percent met the reading benchmark and 15 percent met the science benchmark.
ACT developed college readiness benchmarks with research indicating that students who reach those levels have a high probability of earning a C grade or higher in certain first-year college courses.
The benchmark score for English is 18 or higher. The benchmark in math is 22 or higher, in science it's 24 or higher, and in reading it's 21 or higher.