Tennessee education officials have a new reason to say the state has the fastest-growing test scores in the country.

Tennessee outpaced almost all other states in gains on a science exam administered by the National Assessment of Educational Progress, or NAEP, between 2009 and 2015, according to results released on Thursday.

On average, fourth- and eighth-graders across the nation posted 4-point gains on the 300-point test, administered to a sample of students in most states in 2015. Tennessee students saw their scores grow twice as fast.

“I’m a little biased, but I think the eyes of the nation are rightfully on Tennessee students and teachers,” said Gov. Bill Haslam.

The gains mean that Tennessee fell solidly in the top half of states on the test. Even so, nearly 60 percent of its students did not meet NAEP’s threshold for being considered “proficient” in science.

NAEP is the only ongoing assessment of what U.S. students know in different subjects. It calls itself the Nation’s Report Card because it’s the only platform to compare students across states. Recently, states have cited gaps between NAEP scores and scores on their own tests to toughen their academic standards and exams.

The latest science scores come after many states, including Tennessee, overhauled their reading and math standards and renewed attention to science instruction. Schools and districts nationwide have invested in what they are calling STEM education, an acronym that describes a new approach to incorporating science, technology, engineering and math into the school day.

The U.S. Department of Education has encouraged the shift, launching a program to recruit science teachers and expand computer science instruction.

“The data themselves don’t tell us why we’ve seen these improvements, but we do think investments we’ve made over the past eight years have made a difference,” Education Secretary John King said.

The next phase, King said, is for high schools to add more advanced science and math courses — something for which the new federal education law earmarks extra funding.

“We know from our civil rights data that there are many students who attend high schools where you can’t even take Algebra II or physics,” he said.

Education Commissioner Candice McQueen says Tennessee already offers more rigorous math and science courses than other states, noting that Algebra II is a graduation requirement.

The state’s score increases mean that Tennessee performed better than more than half of other states, which Haslam called “a rare space” for his state. Only 18 states had average scores higher than Tennessee in fourth-grade science, and 20 did in eighth grade.

Tennessee has a goal to be in the top half of states on the Nation’s Report Card by 2019 for all tested grade levels. It inched over that threshold in fourth-grade math when those scores came out last year. This round of science scores means the state is halfway to its goal.

McQueen credited improvements to Tennessee’s English and math standards with helping students achieve in science, too. The state had not touched its science standards for nearly a decade — until last week when the State Board of Education adopted new standards that will reach classrooms in the 2018-19 school year.

“For a long time, Tennessee has had embarrassingly low results in the Nation’s Report Card, often ranking in the low 40s,” McQueen said. “We knew we had to improve quickly, and this would be a stretch. After all, the rest of the country is trying to improve, too.”