<p>My S did not have any placement tests except in Foreign Language.</p>
<p>In his case, as an Engineering major, he wanted to continue with his language but didn't want to place into the very highest level he could possibly reach. Ergo, no prep; idea being to land in an appropriate but comfortable level.</p>
<p>Seems to me if the kid would hate having to "go backwards", such as in the math examples given, it's worth brushing up but not stressing. So that you don't have to repeat material you've mastered.</p>