Do prep schools like Loomis, Deerfield, Exeter Do Math Placement Tests in 9th grade?

I honestly don’t know if tests were online or paper. I’d guess paper pre-Covid and online during. I do know that youngest had to be asked additional math questions by the chair. The school has a rule/maybe based on experience that if Freshmen/first years are going to take an AP that they are well prepared.

I also know that they looked at the previous classes taken. Kid had never taken trig due to change of schools and skipping Alg I in 7th grade. S/he learned it online via Khan. They asked a lot of trig questions.