BIG caveat that these scores are adjusted for gender, age, and race or ethnicity, free and reduced-price lunch receipt status, special education status, and English language learner status. In terms of raw scores, Mississippi is still in the bottom 10. Not really that impressive IMO.
Just grabbing one highly adjusted score and drawing conclusions solely off of that is not enough. It's really only giving you one piece of a very complex puzzle in the case of something like education scores.
Observational stats in social sciences turns out to be a lot like epidemiology and strongly held conclusions are hard won.