An honest evaluation of such things would facilitate the efficient use of educational resources. Not from the standpoint of "those people are as dumb as rocks, so don't spend any resources on them", but "if we're going to spend a certain amount of money on a person's education, what should we do to maximize the benefit that person receives".
To be sure, carelessness or dishonesty in the evaluation of people's intelligence, or in the use of such evaluations, is likely create self-fulfilling prophesies of low expectations. On the other hand, if attempts to teach a person advanced subjects are going to be futile, it's possible the person would receive more benefit if the resources were put toward teaching something they could usefully learn.
Lots of truth there. I read somewhere that a good predictor of a person's ability at high-level manufacturing work is his/her score on a basic algebra test.
I certainly wouldn't use it as the only evaluation, but an algebra-based evaluation makes some sense to me. And it is something that you can improve upon with enough perseverance.