If it's true they are from out of state they are just people passing through the state, not commuters on their way to work each day. However significant amounts of the passenger vehicle traffic there is intrastate and intracounty, as can be seen both from the existence of much more traffic during the morning and evening rush hours, and also the traffic thinning out once it leaves the city.

> If it's true they are from out of state they are just people passing through the state, not commuters on their way to work each day.

Have you looked at a map of where this school is [0]? It's literally between the Washington/Oregon border and downtown Portland. Why wouldn't there be a large commuting population in the Wash State Portland suburbs into downtown Portland?

I'm not deeply familiar with Portland's geography, but it sure looks to me like the urban area goes right up to the Columbia river, so "the traffic thinning out once it leaves the city" would likely be... in Washington.

[0] https://www.google.com/maps/place/Harriet+Tubman+Middle+Scho...

I know exactly where it is. It's several miles south of the border and all of this intermediary space - in Oregon - is taken up with very high density city, mostly residences. In these residences are people who work in Portland and drive to work each day, taking the several on and on ramps along this route. As you drive south through this area in the morning, there is heavy congestion at each on-ramp as people are getting on 5 to go south to work. The school is also directly south of the 405 exchange and north of the 84 exchange, both being major point of congestion that daily intrastate and intracity work commuters use extensively.