[silverlake]

If you look at the full table of NAEP scores, you see the differences are not that much. 8th grade reading is 245(WV)-266(MA). That's 20 point spread, where NAEP goes to 500 pts. A 4% difference between the best and worst state is insignificant. They all suck because they are at 50% of the scale.

[happyopossum]

From TFA - a 10 point gap in NAEP represents approximately one grade level, so your 21 point spread is the difference between 3rd and 5th grades.