High school growrth, 1990-2007

After yesterday's scatterplots of college and graduate school growth, I thought that for the sake of completeness, I should look at the same figures for high school. I was assuming I would have a pretty similar scatterplot.

And I was mostly right, although the correlation is less defined here, and there is a significant group of outliers. Also, much as with the college and graduate school graphs, this is a pretty good repudiation of the "Saturday Night Live syndrome" about US education---Americans are more educated than they were in 1990. (Although, of course, someone can always "prove" via an e-Mail forward that students in the 1950s all learned calculus and Latin in 8th grade, so our educational system was stronger then).
The rate of high school graduation increase varied from 4% in Alaska, to 24% in Kentucky. Which would seem to be bad news for Alaska, besides that Kentucky's numbers are still below what Alaska's were in 1990. The greatest growth was in the southern and Appalachian states that were the furthest behind, while the slowest growth was in states where the rates were already the highest. There just aren't many people left in Utah or Alaska that could get diplomas that don't have them already. The other slow-increase states are the states in the lower-right of the diagram: all four states that border Mexico, and Nevada. I imagine this is the result of Hispanic immigration, since recent Mexican-American immigrants tend to have low graduation rates.