If everyone's score is truncated at 800 on a test out of 1200, then you can't tell the difference between a group that averages 800 vs one that averages 1100
My son did miserably on the ACT the first time he took it and didn’t meet the minimum to get into his college of choice.
After 10 sessions with a private tutor who was a college professor - costing $100/hour - he scored well enough to get admitted. Did he learn anything from the tutor that would help him do well in college or was he taught the test? The test did not measure his aptitude.
Another anecdote. I had the highest SAT score in my school and the second highest in the (relatively poor) city I grew up in. Do you think it was because I was that smart or because my mom was a high school math teacher who had been doing SAT tutorials for years?