[_h4xr]

My impression was that it's pretty rare to move more than half a standard deviation by using test prep. And that median is skewed by the fact that scores fluctuate from one session to another, but the lower scores are discarded.

[byoung2]

I went from a 1340 to a 1520 after a Kaplan course when I was in high school. On the average, massive score improvements are rare, but there are definitely some test prep teachers who can consistently get better score improvements from students. The secret is tailoring your approach to different students' needs. I always looked at the types of questions my students got wrong to identify patterns. If you can fix a bad habit you can get bigger score gains with less effort. My best success story was a student who went from a 980 to a 1420 (out of 1600). That's about 50th percentile to 95th percentile. Another student went from hoping to meet the NCAA minimum for a baseball scholarship to getting an academic full ride. The last student I taught almost beat my score...I took the new SAT in 2005 along with him and he got a 2180 out of 2400 (I got a 2280...99th percentile).