Many parents were understandably alarmed by this week's headlines that Minnesota student reading scores had "plummeted'' this year compared with 2012.

Turns out there's an understandable reason for the double-digit percentage drop. This year a new, more difficult test was given — in other words, the two sets of results were not an apples-to-apples comparison.

The test result confusion highlights an ongoing issue in Minnesota. For political and other reasons — some of them necessary and some not — there have been lots of changes in standardized tests over the years. It's time for the state to settle on strong education standards and exams — then stick with them long enough to make the results meaningful.

The newest round of results from annual statewide tests released this week by the Minnesota Department of Education showed the percentage of students in grades three through eight and 11 who were proficient in reading fell to 58 percent from 76 percent. In math, 61 percent of students who took the Minnesota Comprehensive Assessments (MCAs) were proficient, down from 62 percent last year.

State Education Commissioner Brenda Cassellius dismissed the significance of the results. "Our scores didn't go down," she said. "It's a new, more difficult test. … Our kids didn't get dumber in one year.''

Yet the dip makes a point about the state's overall approach to testing students. Since the mid-1990s, Minnesota has been changing standards and tests on what students learn and need to know.

Years ago, the state adopted an ­outcome-based education model, then shifted to the controversial Profiles of Learning assessment. After that, an eighth-grade basic skills test was put in place, only to be replaced by the current MCAs.

Earlier this year, legislators voted to scrap the Graduation Required Assessment for Diploma (GRAD) exam, which students had to pass in order to graduate. It will be replaced with a series of tests beginning in eighth grade that will be more aligned with postsecondary requirements.

The idea of those ACT-type tests is to measure whether students are ready for college and career training. That should reduce the amount of remedial work teens are doing now.

On top of those state changes, during the past decade requirements mandated in the federal No Child Left Behind legislation added a layer of reporting. And now many states are adjusting their tests to align with the Common Core Standards — a national initiative that seeks to define reading and math skills as students move through the grades.

Minnesota adopted national Common Core State Standards for reading and writing in 2010, but administered tougher tests aligned with those standards for the first time this year. All those shifts have made it difficult for students, families and educators to adjust. Just when they get accustomed to one set of standards and tests, another one comes along.

Fortunately, state education officials say that Minnesota should have more useful, properly rigorous standards and tests in place by spring 2015, when a revised math test will be completed for grades three through seven and a college/career ready high school exam will be given to eighth- through 11th-graders.

The MCA scores released this week once again showed troubling disparities between white students and students of color. Only around 30 percent of black, Hispanic and Native American students met or exceeded reading proficiency standards on the exam. That translates into tens of thousands of young people without a basic skill they need to secure living-wage jobs as adults.

Minnesota kids must be able to compete with their peers not only from other states, but from around the world. To ensure that this happens, it is critical to measure their achievement effectively as they move from grade to grade.

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An editorial of the Star Tribune (Minneapolis). Follow the editorial board on Twitter | Facebook | Pinterest | Google+