PORTLAND — The country’s elementary and middle school students are posting big gains on national math tests— but those in Oregon aren’t quite making the grade.

New data from nationwide math and reading tests show mixed results for Oregon teachers, students and parents: The state’s fourth-graders and eighth-graders aren’t slipping below results from previous years on the tests, but they aren’t showing any statistically significant gains, either.

That’s sobering news in a state that pours nearly half of its two-year budget, upward of $6 billion, into public schools.

Big gains aren’t impossible to achieve. Massachusetts, for example, has made significant progress in raising both math and reading scores, at both the fourth-grade and eighth-grade levels. That state’s students consistently rank at the top of the national heap.

The results suggest a disconnect between the national test, which is given to a sample of 700,000 fourth- and eighth-grade students, and the standardized tests, developed in Oregon, that are given to every Oregon student aged 8 to 13.

The in-state tests consistently show that 70 percent to 80 percent of third-, fourth- and fifth-graders are hitting state testing targets, a generally rosy picture for elementary schools.

But the national test, which is considered the best barometer of how students stack up against each other state by state, paints a far less cheerful picture.

Oregon is in the bottom tier of states when it comes to its fourth-graders, alongside more familiar backbenchers like Kentucky and West Virginia.

According to the results of the national tests, in reading, Oregon’s fourth-graders scored lower than students in 35 other states and significantly ahead of students in just six jurisdictions, remaining virtually tied with the remaining locales.

State education officials have acknowledged that it has been too easy to pass the local tests given to elementary school students, creating an impression that students are doing better than they really are. This spring, the scores were adjusted, making it more difficult for elementary school students to earn a passing grade.

“Oregon’s assessment reflects what folks in Oregon, teachers and others, feel students should know,” said Elaine Hultengren, the Oregon Department of Education’s coordinator for the national test.

There has been a push in Oregon to require students to take a nationally developed test — like the SAT — rather than the local version, but most of those efforts have been concentrated at the high school level.

Meanwhile, middle school students, though their scores didn’t budge much from 2005, are the comparative bright spot for Oregon in the national testing results. Only 11 locales posted math scores that were significantly higher than those earned by Oregon’s eighth-graders, and only eight states beat out Oregon’s eighth-grade readers.

That tracks with improving in-state testing results, said Hultengren. In the most recent round of state tests, 69 percent of eighth-graders were reading at or above grade level, a 3 percent increase from the year before.

Other areas remain persistent trouble spots, in Oregon and across the country. Black and Hispanic students at both grade levels continue to lag their white counterparts in Oregon, sometimes by gaps as wide as 32 points, out of a total of 500. Students who qualify for free or cut-rate school lunches — essentially, those from poorer families — also posted lower than average scores.

Though Oregon students haven’t made much progress since 2005, the last time the national math and reading scores were released, long-term progress is more promising for the state.

For example, in 2007, 35 percent of Oregon eighth-graders got the equivalent of an A on the national math test. In 1992, just 21 percent hit that target.