US segregating by education?

That is the worry expressed by Robert Gallardo and Bob Bishop over at the Daily Yonder.  They are particularly concerned with rural America:

In general, rural areas are falling behind the cities in terms of the percent of their adult populations with at least a college (B.A.) degree. (Scroll down [in the original post] to see maps and lists of the rural counties with the highest and lowest percentage of adults with B.A. degrees.)

In 1990, 23% of adults in urban counties had at least a B.A. degree. The rural rate in that year was 12.4% — approximately half the urban rate.

By 2009, an estimated 29.9% of urban adults had earned at least a B.A. degree. The rate in rural areas had increased to 16.8% of adults. The gap in B.A. attainment between urban and rural counties had increased from 10.6 points to 13.1.