I disagree that is “not applicable” but as I said, just a hunch/hypothesis. It def requires experimenting and research to prove whether it is or isn’t a proxy, at least for this case.
Literally, if you drop out you are no longer eligible to register for any classes. That has no application to determining that low performers are forced into earlier classes.
The other part where high performers are given preference could be.
That’s what I meant by “self-fulfilling prophecy.” High performers are given preference for the “better” times and teachers while low/struggling performers are not.
