I grew up in Seattle, graduated about 10 years ago. Co-ed PE all the way, end-to-end. Separate locker rooms in middle/high school (in primary school it was just a matter of going to play, which is no different than any other day, right ). My brother is 16 now and having the same experiences here (eastern WA).

We had uniforms in middle school that they introduced my second year there, just cotton shirts and loose fitting shorts (that held true through my brother and sister who went through a few years after me). In high school, there was a dress code of basically the same thing, but no uniform. My brother went through the same thing recently, also a super-basic uniform of cotton tshirt/loose gym shorts in middle school and when he got to high school he just used a tshirt and the shorts he used in middle school.

Team sports are separated, of course, but neither of us are really team sports kind of people