Not the best overall picture here in Portland, but there are some options for good schools.
For middle-schoolers, there's the Summa program in suburban Beaverton, which is housed in four different Beaverton middle schools. All eligible students are accepted. It used to be that students had to score in the 99th percentile in reading and in math (or quantitative and verbal, etc.) but now it's 99th percentile in one and 97th in another. Last I heard, the program uses the cogAT and ITBS as determiners. IF the student scores in the 99th percentile overall on the cogAT, he/she is in; if not, then the student can take the ITBS and score in the 99th percentile in either math or reading and then 97th percentile in the other.
As mentioned, there are multiple good private schools in the area, headed by OES and Catlin Gabel; my child attends Oregon Episcopal School and the school has a terrific educational program but perhaps not one that's necessarily for highly gifted learners. We ourselves chose between Catlin, OES, and Summa and picked OES since the Summa program ends after the 8th grade and we didn't want to go through the admissions process again and because OES is more structured than Catlin's program and is probably a better fit for our child's needs.
In addition, several schools in the Bethany area educate the children of the many Intel Ph.D.s living here and as one would expect, there is a higher than expected number of highly gifted learners in that population. The Bethany schools operate much like private schools in their overall level of education and in the overall number of children who will be similar to your own child. The students in these schools test very highly on state standardized tests.
Lastly, there's the International school of Beaverton (ISB) as a middle school and high school option as well as the School for Science and Technology and the Art and Communication magnet school. Other private high school options are Jesuit High School, the Northwest Academy, St. Mary's Academy (all girls), and Valley Catholic school.
I really wish the Summa program could extend from 6th to 12th but that's not really the case and as others have mentioned, Portland isn't a go-to place as far as instruction for gifted students is concerned.
