OMAHA, Neb. (AP) — Nebraska officials are taking steps to improve the state’s education testing scores, starting by adopting new, more rigorous standards.

About 68 percent of Nebraska public school students tested as proficient in science last spring, down 2 percentage points from 2016-17 and 4 percentage points from 2015-16, the Omaha World-Herald reported . The scores were taken from fifth, eighth and 11th grades.

The state is moving to a new science test to reflect changing standards that come with the Nebraska Student-Centered Assessment System. The current test is measuring students’ proficiency against old standards set in 2010, not the new standards the state Board of Education approved last year.

High school students are also taking the ACT exam for the 11th-grade assessment, which may also be more rigorous.

The temporary disparity between the standards and the test could be a factor in the drop, said Nebraska Education Commissioner Matt Blomstedt.

Districts have likely been adjusting curriculum for when the new testing standards are adopted in 2021, Blomstedt said. The new standards raise expectations around science, and will challenge students to think and act like scientists, he said.

“It’s not just about content mastery but the engagement with science content,” Blomstedt said.

The state has also changed standards for English language arts and math proficiency, so schools may be focusing their attention on those subjects, he said.

Changing the testing standards can be difficult, but Blomstedt said state officials believe the increasingly challenging proficiency targets will help measure students’ academic growth.

“The proficiency levels that we’ve set, I would say, are probably among the highest in the nation,” he said.

John Witzel, president of the Nebraska State Board of Education, said schools are working to promote science, but districts are having a difficult time finding science teachers. The western part of the state in particular is seeing a high demand for science teachers.

“I think that might be part of it,” Witzel said.