A decline in local students' scores on a major college-readiness test is hard to diagnose but distressing nonetheless.

If there is any good news, it's that the decline in Terrebonne and Lafourche students' average ACT scores was slight. From last year to this year, Terrebonne's average dropped from 19 to 18.5, results released last week show. In Lafourche, it went from 19.7 to 19.2.

The trend was similar for the state and national average. For Louisiana, it's another in a long-running list of measures in which the state brings up the rear when it comes to young people's academic achievements. Louisiana's average, 18.8, ranks 49th among states, down from 19.2 last year, when it ranked 45th.

The highest score a student can receive is 36. The national average this year is 20.8.

Terrebonne and Lafourche students, then, score better than the state and not far behind the national average. So the latest decline is no reason to panic.

But there is bad news too. These scores include both public and private students. Catholic schools comprise almost all of those students locally, and their average score, 23.5, is higher than both the state and national average.

It is the public schools, those that educate the vast majority of the community's young people, that trail the state and nation. And the overall scores for both parishes would be even lower if the private schools were not included.

Critics note that standardized tests are only one way -- some say an inferior one -- of measuring student progress. And in some ways they make a convincing case. But that should not be an excuse for anyone -- parents, teachers, principals, administrators or communities at large -- to accept mediocre or declining scores. While both local parishes are in the top third or higher among Louisiana school systems, they are doing so in a state that ranks almost dead last.

Some officials point out that Louisiana is among only 15 states that require all high school students to take the ACT. And most of those states core lower than states that only give the tests to college-bound students. But that, too, is too easily used as an excuse. Even among those 15 states, Louisiana ranks 13th.

Public school school officials locally and statewide note that they are working to determine weak spots and address them with additional test preparation and other adjustments. And it's important that they succeed. ACT, the nonprofit that administers the test, offers recommendations that include specific teacher training, school policies and other approaches aimed at improving not just the scores but the knowledge and learning potential they seek to measure.

In a report accompanying the latest scores, the group notes that all students -- not just the college bound -- benefit from a challenging high school curriculum that includes four years of English and three years each of math, science and social studies.

“Our findings once again indicate that taking core courses in high school dramatically increases a student’s likelihood for success after graduation,” ACT CEO Marten Roorda said in a prepared statement. “That’s why we need to ensure that all students of all backgrounds have access to rigorous courses and that we are supporting them not only academically, but socially and emotionally as well.”

And that means the way forward is not lowering standards, or teaching to the test. Instead, it's offering rigorous, challenging courses to every student and giving them the direction, tools and guidance they need to succeed.

-- Editorials represent the opinion of this newspaper and not any single individual.