The adversity score does not affect your SAT score. It is provided in addition to the SAT score and tells the schools considering the student a little about the student’s socioeconomic background. If you are a disadvantaged student, any schools you’re applying to should already know about it (you should tell them).
If you aren’t disadvantaged, and you move to a poor area to get a better adversity score, you have to consider whether that’s worth it. That seems extremely unlikely to me, even if the school doesn’t notice that you’re not poor (which it likely would).
As far as 4S vs. CV, I highly doubt there’s enough difference to matter in any way. But I’m no expert, and I really don’t know. If I were in your shoes, one thing I would do is to see what colleges kids from those places are going to. My daughter just graduated from Canyon Crest Academy, and quite a few of her peers are going to Ivy league schools, MIT, Cal Tech, Stanford, etc.
It does seem notably hard to get into the better UCs from CCA. I don’t know whether going to a crappy school district in National City would improve one’s chances or not. Plenty of kids from CCA got numbers in the range of 35 ACT, 1550 SAT, 4.3 gpa, with good essays and plenty of extracurriculars and did not get into some (in some cases any) of the the mid-tier UCs (Santa Barbara, Davis, San Diego, Irvine). I have a hard time picturing kids from National City with similar resumes not getting into all the UCs, including L.A. and Berkeley. I don’t know what the UC situation is in 4S.
An advantage to better school districts, in addition to better resources, better teachers (theoretically) and more parental involvement/encouragement/motivation/pushing (with its pros and cons) is the pressure to keep up with your peers. Not peer pressure (pressure purposefully applied by peers) so much as just the desire to keep up with them (not sure if it’s different or not…) If a student cares about such things (and most of them do), it seems to me they’d be more likely to push themselves at a school where a preponderance of students seems to be aiming for the likes of Harvard and Stanford and Cal Tech and a lot of them hit those targets while many others “settle” for UC Santa Barbara or Vassar (or similar excellent schools).
