Scores in Iowa are slipping on an exam used to measure the readiness of students for college.

About 68% of Iowa students in the graduating class of 2018 took the ACT last year and they averaged a composite score of 21.8 out of 36. That’s slightly better than the national average score of 20.8, but the data released by the Iowa City-based ACT organization shows scores in Iowa have now dropped three years in a row.

The percentage of Iowa students meeting math benchmarks has dropped from 48 to 44% since 2014. Just 45% of Iowa students who took the test last year are considered ready for college-level science, according to the ACT report. Thirty-percent of 2018 graduates in Iowa met all four ACT college readiness benchmarks.

A total of 24,208 Iowa students took the ACT last year. Twenty-six  of those students posted perfect scores.