So this got me wondering and in my 10 minutes of research I found this. According to Educationbug.com there are roughly 251,000 males in the public school district in Mississippi. Divide this by 12 grades and you get around 20,833 males per grade. But I am sure there are fewer high school seniors than most other grades so let's just take 80% of that number which is 16,666. It also states there are roughly 3000 high school seniors in private schools in Mississippi. (This could also include private schools that play in the MHSAA.) Divide 3000 in half for roughly the amount of males. This gets you to 1500. I went to the Ole Miss website and looked up their current football roster. 5 played at MAIS schools with one from SBEC (private school that used to be part of MPSA and a St. Andrews and St. Jo Greenville guy) If you take 5 and divide it by 1500 male seniors in private schools you get approximately .34%. There were aproximately 30 players that played at MHSAA schools. Divide 30 by 16,666 this gives you .18%. There are more MAIS players % wise on the Ole Miss roster than there are MHSAA. This isn't sabermetrics or Moneyball, but that's some rough numbers I got. If you have anything different please show me. Players from MAIS were Denny (JA) Holder (Sylva Bay) Keyes (JA) Prewitt (Sylva Bay) and Ritter (JA)
UM was 2-10 last year for more than one reason, not having as good a roster as their fellow SEC brethren being a major factor. If one were to examine all the MPSA football players who went D-1 over the past ten years, that might be a more representative sampling and yield a better approximation to answering the question. I personally don't know, I will say that it would stand to reason that punters and kickers from MPSA could be expected to statistically over-represent versus the general public school averages of the same position as that skill can be developed more finely with more family resources, compared to, say an offensive lineman. Possibly the same argument could be made for the QB position, I don't know. The negatives to playing at a small school (less publicity, a wider disparity of overall talent levels of fellow players, ect) work to negate some of the advantages of a higher average household's disposable income for potential MPSA college football recruits.
Interesting question, there's no AAU ball or club soccer parallel in football.