Why are people jumping through hoops trying to imagine possible reasons for differences in academic performance when the best predictor is IQ and that can be me

Why are people jumping through hoops trying to imagine possible reasons for differences in academic performance when the best predictor is IQ and that can be measured from just a few years of age - before they would have to spend time studying or taking care of younger siblings. We already know that east Asian children have higher IQs on average than whites. That explains their better test scores at school. We also know that blacks have lower IQs than whites which also explains their lower test scores. So if you're looking for a cause of the different outcomes, you should look for the cause of different IQs. Since that starts young, maybe black parents don't hug their kids as much as Asian parents (that affects IQ) or maybe it's genetic (that affects IQ). The popular Raven's matrices IQ test has no words, just abstract images so there's no language bias there. Researchers have studied this to death over and over again for 100 years and they keep successfully reproducing the same results. They try everything to eliminate bias, such as having the test administrators be the same race as the subjects and controlling for socioeconomic status and going to different countries and controlling for the economic status of the country and so on. It's a solved problem down to the IQ level. What's not solved is how to improve the IQ of a person after they're born. You can improve it before birth by choosing parents with high IQs.