PORTLAND — Of the 10 states that gave Smarter Balanced academic achievement tests to their students in 2019, Oregon showed the second-worst math performance, behind only Nevada, a new analysis shows.

No other state’s students showed as little mastery of third- and fourth-grade math as Oregon’s did.

Smarter Balanced tests were created more than five years ago to measure the more challenging reasoning skills and problem-solving called for under the Common Core standards now in use nationwide. Students in Oregon and nine other states have taken that exam for five straight years to measure school success in helping students master Common Core skills in reading, writing, math and reasoning.

In addition to Oregon, states that give Smarter Balanced tests are Washington, Idaho, Delaware, California, Connecticut, Hawaii, Montana, Nevada and South Dakota.

Together, they account for 20% of the nation’s students.

Among the 10, Oregon ranked fourth from the bottom in reading and writing, ahead of California, Montana and Nevada.

Oregon’s fourth grade reading and writing performance was the worst of any state by a long way. But Oregon eighth-graders beat the average rate among the 10 states.

Oregon stood out for the lack of progress its students have made in the five years the test has been given. Most of the states improved their performance this year compared to 2018. Oregon, by contrast, recorded the second-largest drop in math proficiency and the largest drop in student mastery of reading and writing.

The analysis was performed by Douglas McRae, a retired California educational measurement expert with a Ph.D. in quantitative psychology who helped develop numerous standardized tests and served as a technical adviser to state testing programs. He gathered and compared scores from grades three through eight. He did not include high school scores, as states give the high school exams in different grades or not at all.

Students in Washington’s public schools led the field in both English and math, besting students in the nine other states, his analysis showed. Connecticut and Idaho registered the next-best achievement in both English and math.

McRae acknowledged there may be some differences in test administration or reporting practices across states. But he said the comparability of scores is sufficient for general comparisons.

Rates of child poverty do not seem to explain Oregon’s poor relative performance. According to Census Bureau estimates from 2018, Oregon has an average child poverty rate among the 10 states as a whole, with Delaware, Nevada and California all recording substantially higher child poverty rates than Oregon.