IQ tests being invalid is more politics than science. Among other things, rejecting the existence of cognitive inequality is necessary to justify systemic racism via the continued existence of Asian quotas (Affirmative Action). Since lots of people benefit from this racism, there’s a huge interest in denial. In western countries, when there’s a few billion people in Asia, and you let a tiny amount in gatekeeping them on the basis of education/wealth/skills, it isn’t really all that much of a shock that they and their children are smarter then average. The only way this could NOT happen is if Asians were LESS intelligent than other groups on average.
IQ tests are hilariously predictive of success if you’re doing a task which is similar to taking an IQ test like academics. They strongly indicate certain mental disorders. Low IQ is more predictive of success than High IQ. Maybe people take the difference between scoring a FSIQ of 110 vs 140 entirely too seriously, but the difference between somebody with 60 vs 90 is staggering.
IQ tests are weakly predictive of academic success, especially on the high end (1SD+). In general, it only predicts 8-25% of variance, even when looking in both directions. That's pretty bad, an average exam does a far better job.
Additionally, the IQ of second generation Asian immigrants will revert to the mean. Not only that, but the advtange decreases rapidly as they age, while the academic advantage grows. And the advantage to begin with is very small - average Asian IQ is only about 2.5 points higher than for Whites, even looking at all generations together.
Given the impact of early childhood environment on IQ, and the huge disparity in academic effort across cultures, esp. those that constitute Asian immigrants, it's pretty clear that the idea that the disparity in Asian achievement cannot be explained by an inherited intelligence advantage. All the data is much more consistent with a culture that just drives students to study far harder.
This does make the argument that affirmative action is harmful even stronger, actually. There is no need to fall back to terrible science to do it. The idea that IQ isn't terribly useful is because it isn't terribly useful, except in very rare cases for diagnosis. The current scientific consensus is consistent with an even stronger argument that AA unfairly discriminates against Asian students.
Not OP, but I understood that to mean any difference in IQ below average (100) has a high impact on success, but differences above 100 have relatively less impact
IQ tests are hilariously predictive of success if you’re doing a task which is similar to taking an IQ test like academics. They strongly indicate certain mental disorders. Low IQ is more predictive of success than High IQ. Maybe people take the difference between scoring a FSIQ of 110 vs 140 entirely too seriously, but the difference between somebody with 60 vs 90 is staggering.