First, a few comments from pieces FTA:

> Plomin’s argument is that, in a society with universal education, the greatest part of the variation in learning abilities is accounted for by genetics, not home environment or quality of school – these factors, he says, do have an effect but it’s much smaller than is popularly believed.

It's important to recognize that in this model, the hypothetical control group is also treated with a very high quality[1], universal, education.

> He finds that genetic heritability accounts for 50% of the psychological differences between us, from personality to mental abilities. But that leaves 50% that should be accounted for by the environment. However, Plomin argues, research shows that most of that 50% is not attributable to the type of environmental influences that can be planned for or readily affected – ie it’s made up of unpredictable events. And of the environmental influences that can be moderated, much of it, he argues, is really an expression of genetics.

I'm not sure where that 50% figure comes from, it seems rather generous. Nonetheless, I'll accept it for argument's sake. It's not unreasonable to split nature and nurture roughly 50-50 as a sort of rough bayesian prior.

Nonetheless, this touches on genetics as a confounding factor for environmental factors. More on this here: [2]

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I could go fishing for papers that contradict yours, but I think it's perhaps more helpful to switch perspectives a bit. Think of this as extra information, not a rebuttal. At the international scale, access to education's impact on vertical mobility is huge, and this difference overshadows the influence of genetics.[3][4] IMO the macro perspective on education helps!

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Edit/addendum. I did go on a little fishing expedition, and found this very helpful: [5]

Selected extracts:

> When environments are homogeneous for all, all individual differences become heritable. [...] Moreover, even highly heritable traits can be strongly manipulated by the environment, so heritability has little if anything to do with controllability. For example, height is on the order of 90% heritable, yet North and South Koreans, who come from the same genetic background, presently differ in average height by a full 6 inches.

> The discovery that all behavior is partially heritable transformed psychology, but, ironically, it also transformed behavior genetics. Once we accept that basically everything—not only schizophrenia and intelligence, but also marital status and television watching—is heritable, it becomes clear that specific estimates of heritability are not very important. The omnipresence of genetic influences does not demonstrate that behavior is “less psychological” or “more biologically determined” than had originally been thought; rather it shows that behavior arises from factors intrinsic as well as extrinsic to the individual. The real implications of heritability lie not in questions of relative biological determinism but in revealing the need to understand both the mechanisms through which the individual, whether consciously or not, directs his or her own life course and his or her power to do so.

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[1] from a historical perspective

[2] https://www.nature.com/articles/s41539-020-00079-z

[3] https://ourworldindata.org/better-learning

[4] https://ourworldindata.org/global-education

[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2899491/