Interesting data.
I do a similar thing, but on a global scale.
My data-set includes 1M+ school websites, 80K+ university websites and another 300K+ for websites of other types of educational organizations. All in all it is close to 1.5M.

On a global scale, WP powers ~24.2% of university websites and 21% of school websites. The global share is very much decreased because of WP’s low adoption in many Asian and African countries.

I also check which plugins, themes and Google fonts are the most popular.

P.S. I made some of this data public here, if people like stuff like this: https://www.ilovewp.com/resources/education/