Comment by Retric

> the numbers I gave you

You didn’t give any numbers, just stated things very confidently without actually reviewing any of the relevant literature.

> the false assumption that moving from each tier is a low probability event

Doesn’t need to be a low probability events, multiply probabilities and the result becomes less likely every single time. And that’s of course ignoring the underlying reasons why the probability at each stage isn’t low in the first place. A smart kid at 6 is unlikely to turn into a dumb kid at 16 etc.