You didn't say anything about school in your initial posting...
Unless less it has changed and it probably has since daughter went thru it...even though she had drivers lic and car registered and registered to vote. When she went to register for school they said she was not a "resident for school purposes" and told her to pay out of state tuition. Until she completed a year in state. (She just postponed school for awhile) This was many years ago and might of been changed by now? I think they look at drivers lic and date of issue???
Student Residency
To qualify as a resident student, state law requires that a student establish a bona fide domicile in the state of Washington for a period of one year
But not sure if its just the place that web page is for or all the state.
http://www.wsac.wa.gov/student-residencyAnd here is more
http://dor.wa.gov/Content/ContactUs/con_residdef.aspxMy best guess is the state wants you to pay some tax before giving you "resident" school rate.
More things to check out.
Good luck