I certainly agree that talented students from disadvantaged backgrounds ought to be helped. But thinking parental income is the causal factor behind the observ

I certainly agree that talented students from disadvantaged backgrounds ought to be helped. But thinking parental income is the causal factor behind the observed correlation of student success with income may be mistaken. Two other hypotheses are that the money itself is not important, but rather the familial transmission of certain cultural traits (which also often lead to high incomes), and/or that, similarly, the causal factor is genetic transmission of some cognitive or personality traits. Note that a factor being genetic does not mean it is immutable - for instance, there could be a genetic factor that leads to students doing poorly in school because they are intolerant of sitting still for hours in desks, which would become irrelevant if one stopped requiring them to sit still for hours. A mistaken idea of the causal explanation for the correlation with income would lead to interventions that don't actually work.