Not a crescent: education patterns in the North East

This blog is becoming increasingly about two numbers: the high school graduation rate and college graduation rates of counties in the US. This could just be my peculiar obsession, but these two numbers together do tell a lot about a county.
It is harder to add them up across states, since "counties" have many different meanings in different states. In the eastern part of the US, counties are much smaller in area, and often much smaller in population.

After I did the Western states, I went through and entered the information for the New England/Middle Atlantic states. Which, for my purposes, are: Maine, Massachusetts, New Hampshire, Vermont, New York, Connecticut, New Jersey, Pennsylvania, Delaware, and Maryland. These states all have relative small numbers of counties, and they also share common demographics, which makes them a good set to compare amongst.
The first thing of interest is that this is not a crescent: the Northeast doesn't seem to have many areas that have high highschool rates and low college rates. It seems to have more of a traditional X=Y relationship. I am also wondering if perhaps I chose the best grouping of states: it seems that what does occur in the lower right might be based heavily around rural Pennsylvania.
Another obvious thing is that there is one major grouping of states, and then a bunch of points to the left. The points to the left make up some really significant outliers. They consist of Sussex County (Boston), three of New York City's burroughs, Philadelphia County and Baltimore City. As could be expected, big metropolitan areas pull in both college educated people, and non-high school educated people.
Also, notice the trio at the top right: two counties in Maryland, just outside of Washington, DC, and Thompkins County, home of Cornell University.