Graduation from a Texas high school after enough attendance can retain Texas residency for tuition purposes. See Texas Residency - Texas One Stop - University of Texas at Austin
What state will they move to? Note that there is typically a waiting period before in state tuition can be gotten.
University of Washington is not the only more accepting area. If you are “grateful to not let the price of the school weigh my decision”, then you have lots of other choices that will meet this criterion.