WRT the eastside of Seattle (Bellevue, Kirkland, Redmond, Sammamish, Issaquah)-all of these (Bellevue, Lake Washington(Kirkland/Redmond/Sammamish), and Issaquah school districts have highly capable programs.

Here are some links to help you:
LWSD: http://www.lwsd.org/programs-and-services/accelerated-programs
Issaquah: https://www.issaquah.wednet.edu/academics/programs/gifted
Bellevue: http://www.bsd405.org/programs/gifted/

Most require standardized testing provided by the school (e.g. Cogat,etc.) The schedules for the testing should be listed on the sites by the end of summer for the 2018-2019 school year.

Let me know if you have questions..happy to help.