Standardized testing isn't actually a measure of intelligence, or of function.

Plenty of intelligent, accomplished people report having been horrible at school, or at doing tests. Sitting, working for the approval of an authority figure, or a series of questions on a sheet of paper just might not be a good way to figure out the smart people from the dumb people... It's really a measure of searching for "good test takers" - a quality that you might not actually want in a society.

"Hey these people work really hard to get perfect theoretical score for the approval of a sheet of paper or a guy in a suit". Uhuh, and the claim is that's "smart"? Okay "boss".

Sometimes we forget the kind of life the education system was built around. We mistake it for something objectively "good". Hell, look at the brutality of the British school system in the colonial era. Education and testing has a Sociological context, and is a system built of the society's purposes/ends.