That's true to an extent, but much less true of Catholic parochial schools. In fact, such schools will sometimes have a population with average income less than the local public schools. Of course most parochial schools won't have special education programs, so that's a huge filter, but as I pointed out doesn't account for the budget gap.

In any event, "picking your customers" is exactly the point of the previous poster(s). Money doesn't really explain what we're seeing. Once upon a time there was a very strong correlation, and people presumed causation, but now it's quite clear that the causation wasn't there. Certainly not directly, which is why throwing more money at the schools isn't helping.