PORTLAND, Ore. – Both Oregon and Portland’s graduation rates rose in the 2015-16 school year, but Oregon remains far lower than the U.S. average.

A closer look at the data shows some Portland schools and metro districts fared far better than others, and the success stories tend to happen in wealthier areas.

Portland’s four-year graduation rates rose from 73.8 percent for the class of 2015 to 75.5 percent in 2016. The state’s graduation rate rose to 74.8 percent in 2016, up from 73.7 percent in 2015.

The average U.S. graduation rate in 2015 was 83 percent. The 2016 data has not yet been released.

In Oregon, big gains were made among many minority groups, but minorities except for Asian students still graduate at significantly lower rates than the student population overall. The graduation rate of African American students rose to 66.1 percent, up 3.6 points. Native Hawaiian/Pacific Islander students rose 6.9 percent to 70.1 percent. Students with disabilities rose 2.8 percent, with 55.5 percent of students graduating within four years in 2016.

Asian students overall fared the best. Their four-year graduation rates rose 0.5 percent to an 88 percent four-year graduation rate. White students had a 76.6 graduation rate.

More female students graduated on time, compared to male students – 78.4 percent to 71.4 percent, respectively.

Economic stability is one of the biggest factors for success. Economically disadvantaged students graduated at a rate of 68.1 percent, while students 83.8 percent of students who were not economically disadvantaged graduated on time.

“We are making progress, while recognizing there is still more work to do," said the state's Deputy Superintendent Salam Noor.

At Portland high schools, the rates weren’t consistent school-to-school. At Roosevelt High School in North Portland, students improved their four-year graduation rates by about 3 percent but still just 64.7 percent of students graduated on time.

Schools in Southwest Portland, as usual, had the best graduation rates. Wilson graduated 90.3 percent of its students on time, and Lincoln graduated 93.7 percent of students.

Interim Superintendent Bob McKean said Portland's graduation rate has risen 20 percentage points over the last seven years and this is the first time Portland schools have surpassed the state average.

"We still have 24 percent that are not graduating and I think about them on an individual basis, what it means to their futures," he said. "If students don't graduate from high school, their earning power is considerably less, their lifespans are shorter."

In the Portland metro area, West Linn-Wilsonville had the best graduation rates, with 93 percent of students graduating on time. Lake Oswego wasn't far behind, with 91.7 percent.

Statewide, 26 Oregon high schools had a 100 percent graduation rate. All of the schools were small. The largest school with a perfect score, Oakland High School in Douglas County, had just 45 students in the adjusted cohort.

Other high schools with near-perfect graduation rates include Henley High School in Klamath County, which graduated more than 99 percent of its 133 students. West Linn High School in Clackamas County, the International School of Beaverton in Washington County and Gervais High School in Marion County graduated more than 98 percent of students.

At the low end of the range, the Mitchell School District in Wheeler graduated just 13.5 percent of its 192 students. Most of those students attended an online charter school called Insight School of Oregon Painted Hills. The Arlington School District in Gilliam County graduated 22.2 percent of its nine students, and 27.1 percent of the 118 students in Douglas County’s Elkton School District graduated on time.

The lowest rates in the state came from alternative high schools. Seven alternative schools had a zero percent graduation rate, and five graduated less than 10 percent of students on time.

Portland High School 2016 four-year graduation rates:

Benson High School 88.83 percent

Cleveland High School 85.7 percent

Franklin High School 85.4 percent

Grant High School 88.8 percent

Jefferson High School 83.7 percent

Lincoln High School 93.7 percent

Madison High School 74.3 percent

Metropolitan Learning Center 91.4 percent

Roosevelt High School 64.7 percent

Wilson High School 90.3 percent

Metro graduation rates:

Beaverton School District: 83 percent

Gresham-Barlow School District: 74.4 percent

Centennial School District: 74.7 percent

Oregon Trail School District: 69.3 percent

David Douglas School District: 75.7 percent

Reynolds School District: 59.3 percent

Hillsboro School District: 81.7 percent*

Canby School District: 88.3 percent

North Clackamas School District: 80 percent

Oregon City School District: 86.3 percent

Parkrose School District: 75 percent

West Linn-Wilsonville School District: 93 percent

Lake Oswego: 91.7 percent

Tap to view the state's graduation rate data

Related: Oregon, Portland HS graduation rates improve in 2015

*Hillsboro School District said the district’s data was incorrectly reported to the Oregon Department of Education and wasn’t changed before the data was released. The district said it graduated 81.7 percent of students, not 77.9 percent, as the state reported.

Dave Northfield contributed to this report.