Yep fair point....seems like the rich get richer and the not so rich get poorer has hit the greater Springfield area.
Just my opinion, but I suspect that college tuition inflation plays a large part in this, as well as the IHSA 30 mile limit. Parents begin worrying about college earlier and any who have kids with athletic ability are looking to get their kids into programs that have a track record of getting kids into college scholarships. You can most easily do this in one of two ways. Move to a school district that does it, or pay tuition at a private school. In Chicago and the 'Burbs, this has been seen for years. But downstate, the decision had to be weighed against counter factors like leaving friends and families or jobs and the costs of moving to a usually more expensive town or home. There is also the perceived stigma and danger of city district schools like Decatur Eisenhower and MacArthur and Springfield Lanphier and Southeast.
In the Springfield area, the choice used to be Griffin/SHG or Chatham, known for high housing costs. But the rise of Rochester and a couple of smaller powerhouse teams like Williamsville and Athens, coupled with galloping tuition inflation at SHG and the odd nature of Springfield District 186, gave families more options. If you don't want to pay the tuition or don't want to send your kid to SHG for religious reasons, moving "to" any of the aforementioned districts has none of the counter factors. It is possible to change districts with negligible moves of only a couple of miles. At least six school districts actually include Springfield neighborhoods. We see it in Decatur also. There the choice is St. Theresa vs sports power districts like Maroa-Forsyth.
And there is no longer a race issue. Schools like SHG and St. T used to be seen, rather unfairly, as not racially inclusive. But as more and more African American students went there and prospered, that mis-perception seems to have disappeared, to the disadvantage of schools like Lanphier, Southeast, MacArthur and Eisenhower.
Unlike Springfield and Decatur with their perennial haves and have-nots, a district like Jacksonville with no options closer than Springfield and no power private programs tends to swing wildly according to the "luck of the draw" in terms of students.
Sorry if this rambles a bit, it's a simple concept but hard to put into words. But the upshot is that the discrepancy between the football haves and have-nots is unlikely to change In the foreseeable future.