Now that
@ashokan has enlightened us, we can return to our regularly scheduled programming.
I corresponded with someone who knows a lot about the LSAT. He says there have been no studies on the effect of prep courses on LSAT score. But there have been studies on SAT scores. The results are significant because there is a strong correlation between SAT and LSAT score --particularly between verbal SAT and LSAT score. (In my case, there was only a one point difference -- I took the LSAT in the ancient days when it was graded on the same 200-800 scale as the verbal SAT.) The studies find that preparation increases scores, but only by a minor amount that would be about a point on the LSAT scale. There are people who get a big gain from preparation, but these are people who are very rusty on basic skills. This is most important for the math portion of the SAT because many kids either didn't understand math the first time around or have forgotten whatever they learned. None of this matters much for the verbal SAT. Most important, it is not necessary to take an expensive course to get the benefit of preparation -- any course, including the free course offered through the Educational Testing Service ,will do. The courses help not so much because they give the kids any specific skills, but mostly because they focus kids on preparing.
We'll see what the ABA House of Delegates does with the LSAT requirement -- and, more importantly, how the law schools react to the end of the mandate. As I said above, law school deans oppose the abolition so probably the vast majority of law schools would keep requiring the LSAT