While this is plausibly correct, it is misleading. Ability is what determines how quickly one can “master” material and under what conditions. There are a few 12 year olds who score 750+ on SAT EBRW, and many more who score that highly on SAT math. Anyone who believes these kids are being “prepped” into these scores is fooling himself.
As the importance of ability is so obvious at the “edge” results (12 year olds with 1500+ scores), why would we think ability plays no role in the more typical score ranges?
The reality is some (relatively few) kids in high school can prep for 10 hours and never score below 1550, while others could prep for 1,000 hours and never break 1200 (also, relatively few I would guess if they actually put in 1,000 hours). I am inclined to believe that a student’s highest potential score is largely a function of ability, while the actual score received is more a function of factors like the willingness to work hard, which itself may also be somewhat innate.
I guess the takeaway for this thread is that parents should not expect miracles from test prep, and should not unduly stress out kids to “hit” a certain number. Most academic studies have shown very limited value for test prep - on the order of 20-30 points total on average for SAT - although admittedly most of these studies are getting pretty old by now.