There's also a "magnet" school [...] in the county seat that seems to only be useful for draining off the non-sports smart kids.

It has been shown that there are benefits to the smart kids to separate them into a different curriculum. Grade skipping has problems as it pushes kids into social situations they meet not be equipped to handle. By creating different tracks, you can have some students take more rigours courses which actually challenge them and so kids can learn the soft skills they wouldn't learn with an easier curriculum. I've seen some high schools where you can basically graduate with a year's worth of college credits.

Which if you didn't know is a way to drain funding from "under performing", i.e., poor, usually minority, schools.

And I would agree that is part of the problem as expressed in the article. Most states are preserving or increasing the teaching quality for high performing students while absolutely collapsing funding for under performing students.