AUGUSTA — Maine’s high school graduation rate grew by more than 2 percentage points in one year, but Education Commissioner Stephen Bowen warned today that there’s still more to be done in a state where nearly 20 percent of students fail to graduate in four years.

The graduation rate for publicly funded high schools grew from 80.4 percent in 2009 to 82.8 percent in 2010, according to the Maine Department of Education.

“While the data show a noticeable improvement over the previous year, we can’t be satisfied when nearly one out of five students who enters ninth grade does not graduate in four years,” Bowen said.

This is the second year Maine is reporting graduation rates under a new system that’s now required of all states by the U.S. Department of Education.

Using the new formula, 88 high schools showed an improvement, 43 saw a decline and two showed no change. Almost half of all schools have a graduation rate lower than 83 percent, the rate necessary to show Adequate Yearly Progress under the No Child Left Behind law.

The new method totals the graduation rate based on the number of students who entered ninth grade at the same time and graduated in no more than four years. Because it only counts students who graduate in four years or less, the state’s graduation rate is lower than under the old system.

While two years of data is not enough to establish a trend, Bowen is hopeful that a move toward performance-based or standards-based education in Maine schools will make a difference in keeping kids engaged.

Performance-based education allows students to advance when they master new skills, instead of advancing all students at the same time. That gives kids who’re struggling more time to master particular skills, while letting others advance sooner, said David Connerty-Marin, department spokesman.

“By setting rigorous standards and allowing students to move through school based on their mastery of skills — not based on arbitrary timelines and seat time — students will be more engaged, their needs will be more clearly met, and more of them will graduate,” Bowen said.