I'd look hard at the tests first. Apart from the question of validity of the measures: it's possible that the standardized tests are not keeping up with the changing ways we interact with the environment.

E.g., how many kids play with blocks these days? Building model skyscrapers, log cabins, model railroads? Outdoor games? -Unstructured- play time?

Quite a bit different from Minecraft, physically and mentally.

Or, possibly the testmakers are modifying the tests, but the new numbers are not readily comparable to the old ones.