I think we're missing each other. Propensity to study may be a different attribute than IQ, which is a predictor for both standardized test scores and academic

I think we're missing each other. Propensity to study may be a different attribute than IQ, which is a predictor for both standardized test scores and academic success. Normalizing for socioeconomic factors does not in itself disambiguate these possibilities. Someone with low motivation to study is not necessarily 'neglected'. I've seen years ago a highly cited paper showing relatively high correlations between SAT scores and IQs, but critically its data was from the late 1970s, when norms around test prep, and access to prep resources, were meaningfully different.