Some people do not do well on standardized tests. My guess is as with most Democrats, Bill is bad at math.
The old joke with the SATs was that you got 200 points just for putting your name on the cover page.
I’ve always been a decent taker of standardized tests, but I know people who are astronomically more intelligent than me who scored abysmally on the SATs. Intelligence is not an objective measure despite what they want people to believe.
It’s like Heisenberg’s Uncertainty Principle: as soon as you observe someone/something, you change it. By testing people, you are putting them under pressure and changing the way they think. Making a test timed put even more pressure on the tester.