Blawg Wisdom posts a question about the way multiple LSAT scores are handled. Yes. Most law schools average them, but if you want to be sure contact the schools individually. I wouldn’t trust the boards with this questions.
The best situation is to prepare, take the LSAT once and ace it the first time, but you all know that and would never consider taking it to "see how you do."
A trackback in the same post suggests that if you do poorly on one administration you provide an explanation and attempt to convince the school to only consider the higher score. It is possible, but difficult to explain away a poor LSAT. If you feel it is worth the effort, use an addendum for the excuse. Let you personal statement provide lots of reasons for them to admit you. Then in the addendum succinctly make your case why the higher score is a better measure of your ability than the lower one because of extenuating circumstances surrounding the rotten score.