After reading this thread and thinking about our midwestern public high school (no magnets in our neighborhood) located in a college town, I think the fact that we have a very prestigious large public university (UMich) in the state satisfies the academic ambitions of most of the most talented students in core subjects.
The ones who wander out of state tend to be either artsy (heading to an art school, or perhaps to NYU for theater), are looking for a small college (better ones out of state than in-state), or a big city environment (which Detroit does not satisfy) – or are looking for an academic environment that’s more focused in some way. If those kids don’t go out of state for college, they are likely nonetheless to go there after graduation. Case in point: of the ~200 graduates in my daughter’s high school class, five years later ~20 of them were living in NYC (specifically Brooklyn). Quite a good-sized ex-Michigander community in NYC. Chicago is another frequent big-city destination for our local graduates. (BTW, there really is something to the Detroit renaissance: more graduates are heading there now than just a few years ago.)
While certainly some of graduates from our HS apply to and attend Ivies, as well as UChicago, CMU, and other high-rep universities outside the state, I think in our town many of the parents (high percentage college grads themselves) have figured that if their kids are going on to careers that require graduate diplomas (law, medicine, business, etc.), they don’t have to attend the most prestigious undergrad institutions, just very good ones. And so the likes of UMich, Denison, Kalamazoo, Macalester, and others are perfectly fine places to get an undergrad degree. And it’s hardly a dead-end to earn a degree from Michigan State, Western Michigan, Mich Tech, or other state or private institutions. In short, we see very little of the “Ivy or Bust” mentality among our high-schoolers.