Unlike the talent search results, the high school ones will stay "on your permanent record" I don't know if that matters or not if the scores are high.
I know that this is many years ago, but I took the PSAT as a Junior, the SAT once as a Senior, got good, but not great scores and was accepted by an excellent, competitive college. My parents were not rich and they were not going to shell out for multiple tests. Most of my friends from college were in the same situation; it really never occurred to us that it was an option to take it more than once. Most of these folks now have advanced degrees.
So, I guess my point is that, if there is something that you are looking for (practice for a person who gets nervous, opportunity to guage progress etc), then go ahead and take it, but if a child doesn't take it as a sophomore, you probably aren't depriving them. Heck, a free Satuday morning and $40 saved are nothing to sneeze at, either!
