You are still eligble for traffic school but you may have to appear for the ticket in Washington to request it and possibly attend traffic school in Washington.
I found the link for you to the Spokane court website.
http://www.spokanecounty.org/districtcourt/
In some cases you can "eMitigate" so you do not have to appear in person. In depends on the details of where you were speeding (school zone, construction zone, etc.) Here is the link to that
http://www.spokanecounty.org/districtcourt/reports/
I couldnt find out if it is approved in Spokane but some counties in Washington allow you to also do traffic school online. You would have to request that from the judge during your apperance or eMitigation proceeding.
