It’s not very good, because it shows that you took it easy. It’s a tiny bit better than having a study hall, but not much, and definitely a minus unless you have a plan with that teacher where you’re going to do specific things and can tie that in to the rest of your app. For example, you’re fluent in German: are you president of the German club, set up an AP German tutoring prep review group coordinated by the German teacher for those who wish they could take the AP, manage the German conversation club, take the most advanced classes offered in your community college, intend to minor in it, are taking online courses from German technical universities? Then adding being TA in German would “make sense”.
TA’ing in a random subject? Not so much.
I can’t help but notice the incredible range of universities you’re considering.
Portland State: non selective, commuter school with a large percentage of adult student (average age at a “traditional” college is about 20, at Portland State it’s 27, roughly the same as in an MBA program where students have 3-5 years of work experience), majority of students transferring in from the community college system.
On the opposite side of the spectrum, Stanford, one of the hardest schools to get into, turns down 95% applicants, most of whom are the most accomplished you can imagine, with national or international-level prizes.
For UO or OSU, taking the TA class period wouldn’t make a difference and if it makes your life easier, go for it. SJSU will not care either, all they care about is GPA X SAT score (or ACT score).
For Stanford, it’d be extremely unwise, but unless your school offers few APs and you didn’t indicate honors level for your classes (ie., unless you know that for this schedule your guidance counselor will indiate “most rigorous offered”), it’s out of reach anyway.
In between, I don’t see HarveyMudd, CalTech (both reaches), Santa Clara,U of Pacific, Cal Poly SLO, CPP, URochester, Olin, RPI, (if you’re interested in STEM fields) or (if not) Occidental, Pitzer, Chapman, Reed, Lewis&Clark, U Puget Sound, Willamette, Whitman, not to mention aren’t you applying to UOregon, UWashington… any reason why?
If that’s because you ran the Net Price calculators and those colleges weren’t affordable, that’s good. 
If not, look into those, because your college list isn’t very balanced.
Typically, you’d have 2 safeties (colleges you like, ran the NPCs for and know your parents can pay for, and are sure you can get into beause you’re well above their 75% threshold), 3-5 matches (colleges you like, ran the NPCs for and can afford, and think you can get into because you’re above the average and closer to the 75% threshold), then as many reaches as you wish or can afford.