Sneaky age filter? You must be young enough to remember your SAT scores.
I can remember mine just fine.
If you're really looking for smart people, use "Answer this word problem in two or more paragraphs. Write your answer on the sheet of paper provided. In cursive."
Are people who were forced to learn cursive smarter? They're just older.
Doing this may well expose you to age discrimination lawsuits, since it's just sneaky indirect age filtering.
Another example would be if you required a minimum SAT score of 1601. Sure, someone could have gone off and taken the SAT as an adult or a young child but in reality it is mainly an age filter.
Having to write the "I did not cheat" pledge in cursive was the most difficult part of the SAT for me.
"In cursive" is just filtering for people old enough to have been taught cursive.
The signal being that the smart people will refuse to jump through this hoop in your inane process because they have a lot of other opportunities to choose from.