I don't think they need to prep for the material, but my daughter was a little unsettled by the tight time limits. She just had not had tests like that before. If I had realized that would be an issue in advance, I would have had her do a practice test or two just to get used to the format.
That said, even with no prep she did fine. She just missed the cut-off, but got into Algebra anyway and is doing well so far.