I can tell you first-hand that you are definitely on to something about the economically disadvantaged schools and colleges. Having worked in Cincinnati Public Schools in past, I can tell you that the top 10-15 seniors in each school's graduating class, get so many acceptances and so much scholarship money, it'll make your head spin. The Valedictorian from let's say Woodward would have multiple full-ride scholarships and only having scored a 21-24 on the ACT.The schools with the big National Merit offers are a tier below Ohio State, Michigan, etc. academically. Alabama, Kentucky, Wichita State, Central Florida, Ole Miss...all schools trying to raise their academic standing.
The problem with National Merit is that the standards are different from state to state. The qualifying score is lower in Mississippi than it is in Virginia.
Being a National Merit Scholar isn't much more impressive than being President of the French Club when Stanford can fill out their entire freshman class with kids that have 4.0 unweighted GPAs and 36 on the ACT and put an entire second freshman class on the wait list with the same stats.
Having a "hook" is more advantageous, and I suspect that graduating from an economically disadvantaged school district is a pretty solid hook. Many of the elite private colleges offer need-based, as opposed to academic, grants and scholarships. If you can get it, it might be cheaper to go to Notre Dame or Northwestern than Akron (assuming you're not a commuter).
I'm not saying it's right or wrong, but Colleges and Universities will bend over backwards and give so much money to poor minorities to diversify their campus. When I was working in CPS, I saw many seniors get paid to go to college because the school gave them a full ride, and then they got tons of outside scholarships, most were only available to minorities. And my experience was that private schools shelled out way more money to students from poor schools, most wasn't "need based aid." (My experience is purely what I saw working in CPS).