I didn't know students still believed this myth. There is not a maximum potential on the MCAT, no upper limit you cannot cross. The AAMC would like you to believe that their exam gives you some magic score that is "your score" and is highly unlikely to change. Not true. Scores change all the time, often dramatically, and bigger reason scores are hard to change is because student behavior is hard to change. Most students retake the MCAT after making very few SUBSTANTIVE changes to what they did to prepare for their first exam, so yes, they end up getting a similar score.
The only limits on your potential are your own behavior, your own willingness to sacrifice and do whatever it takes. You all need to relieve yourself of this ridiculous burden and allow yourself to believe the far more encouraging TRUTH...that *almost* any MCAT score is attainable if you are willing to invest the work necessary.
The reason only 5% of students score a 517+ is not because only 5% of students have the genetic potential to do so, it is because only 5% of students have reached the threshold of knowledge & skills necessary to earn that score. Nearly every other person among the 95% could cross that same threshold, given sufficient time and personal discipline/commitment.
One thing I love about the MCAT is that it is not actually curved in the way people think it is. If 100% of the students on a given test day earn the raw score associated with 525, everyone gets a 525, period. It's like being an Olympic high jumper but knowing that as long as you cross the bar at "x-height", you will receive the gold medal.
I have personally helped a student who did not know his times tables at our first meeting achieve a 90th-percentile score. I've helped several students achieve 20-point improvements. One of my good friends who is now an Altius tutor had taken the MCAT three times and sputtered out around 500, then he got a 523. There is no freaking limit based on some "genetic potential." Bull crap.
This idea seems closely related to the idea that the MCAT is an IQ or aptitude test, when it is neither. Multiple studies have shown that IQ does not predict MCAT score. In fact, personality is a better predictor of MCAT score than IQ. Even if the MCAT was somewhat like an aptitude test, which it isn't, many studies have shown that IQ can be improved through several different methods, such as additional study, mentoring, brain training, etc. A recent study showed that students could increase their IQ by a set number of points for each year of additional education. This myth needs to die. Don't let this silly test intimidate you. Anyone can kill the MCAT if they really want to.