(Salem, OR)  --  Oregon's high school students are lagging behind the national average in advanced placement tests.  The College Board announced yesterday that 18-percent of Oregon's 2017 graduates got a three or better on the five-point grading scale.  Nationally, the figure is 23-percent.  Most colleges reportedly give credits to students who get at least a three on the exams, including the University of Oregon and Oregon State University.