Christopher Phillips, principal at Jefferson-Houston School, visits a second-grade class while walking around the newly built school on September 29, 2014 in Alexandria, Va. The school isn’t yet fully accredited, but its scores have improved. (Ricky Carioti/The Washington Post)

Eight in 10 Virginia schools met state benchmarks this year and 200 schools regained full accreditation, marking the first year of significant improvements since tougher standardized tests led to a slump in scores.

According to results released by the Virginia Department of Education on Tuesday, 351 schools fell short of state benchmarks for having too few students pass standardized tests, or about 20 percent of schools statewide. In 2014, 30 percent of schools missed the mark.

Gov. Terry McAuliffe, speaking at the library of Alexandria’s Patrick Henry Elementary on Tuesday, called the improvements “a major milestone.” Patrick Henry was one of the 200 schools to regain full accreditation.

“We now have 1,414 schools with full accreditation, which is a 10-point boost for us. That is a huge number,” McAuliffe said. “We did it the old-fashioned way. We gave the teachers and the schools the tools they needed.”

The state began to see a drop-off in the number of schools that received full accreditation in the past few years because of the introduction of tougher standardized tests. Last year, nearly a third of schools were “accredited with warning,” up from 22 percent the previous year. Six years ago, just 15 schools got that distinction.

Thirteen schools were denied accreditation altogether last year, the most ever. That number remained the same this year.

Virginia was one of a small number of states that did not adopt the Common Core State Standards, which many argued were more rigorous than previous state standards. Instead, Virginia introduced tougher standardized tests in 2011, leading more students to struggle on the exams and more schools to lose full accreditation. The new exams were supposed to better gauge a student’s critical-thinking skills.

The state began to see improvements across the board in test scores this year, as teachers and students became more accustomed to the new exams and after the state allowed some students to retake exams if they came close to passing.

For schools to be fully accredited, at least 70 percent of students must pass state standardized tests in math, science and history, and at least 75 percent must pass state English exams. High schools must graduate at least 85 percent of seniors. The state makes slight adjustments based on the number of English language learners and also gives schools bonus points when a student who previously failed an exam passes it.

The state also rolled out a new accountability system this year. The benchmarks for full accreditation remained the same, but schools that come close to benchmarks are labeled “Partially Accredited: Approaching Benchmark.” Schools that make significant gains in test scores but still fall short are labeled “Partially Accredited: Improving School.” In the past, these schools would all have been labeled “accredited with warning.”

Seventy-six schools were labeled “improving schools” this year and 46 were labeled “approaching benchmark.”

Northern Virginia schools did considerably better than the state, with just 7 percent of schools falling short of full accreditation. Just one Northern Virginia school, the Jefferson-Houston School in Alexandria, was denied accreditation, though it made considerable gains in test scores this year.

In Fairfax County, the state’s largest school district, 15 of 192 schools this year fell short of benchmarks, down from 17 last year. Two of those schools were labeled “approaching benchmark,” for missing the mark by a narrow margin. In 2012, all of the county’s schools received full accreditation.

Fairfax County Superintendent Karen Garza lauded the state board of education for altering the accreditation standards to give schools credit for improvement and coming close to benchmarks.

“We applaud the Virginia Board of Education for listening to local educators and moving away from an all-or-nothing approach in determining accreditation,” Garza said.

Prince William and Loudoun counties both cut in half the number of schools that fell short of benchmarks between last year and this year. In Prince William, six schools missed the mark and all of the district’s high schools were fully accredited. In Loudoun, just two schools missed the mark this year.

All Arlington schools were fully accredited, with two that were accredited with warning last year moving up this year. In Alexandria, about a quarter of schools failed to meet state benchmarks.