I'm a guidance counselor. There is really no prep for the olsat. It is testing a certain way of thinking, and a person either has the ability to see things/think in that way or they don't. It really is not testing any knowledge (so one can't study or review for it), it is testing Ability. Basically, does a person have the ability to think a certain way to solve a certain kind of problem or see a certain kind of pattern. It is scored a little strangely- no penalty for not completing any problems, but it is timed and the kid gets as far as they can get. The more you get right the better. The scores are scaled by age, down to the month in which the kid was born. There are only a few different types of problems in it depending on the age level, usually it is analogies and patterns and sequences. Eg weird shapes in a row and "what comes next" or "ice is to cold as coal is to ----".
I'm giving this test next week. I'm guessing your kid is taking it to see if they will be identified for GATE (gifted and talented education). The other thing about using this test for GATE qualification is that a school district sets their own bar for GATE qualification. In my district its 98th percentile and up. In other districts it is significantly lower.
If you can't tell by now, I think GATE testing and the olsat are totally arbitrary measures of a kids intelligence. So don't get too caught up in it. The olsat is really looking at just a certain kind of thinker. I wouldn't feel to bad if my kid happened to not be that specific kind d of thinker. It has no bearing on potential for academic success, really. I know plenty of scattered, head in the clouds GATE students who can't get it together in class.
Sorry I just read the answer below mine and that is NOT at all what the olsat is used for. It would not be an apprpropriate way to measure where a kid is academically, what their skills are, or where they should be placed.