Earlier I summarized what I think are the four most often mentioned ideas about why poor kids do worse in school. It is not just school of course: poor kids do worse in any number of ways throughout their life. Among the theories, I think the “effects of poverty” theory has the most plausibility and empirical support. I summarized that theory thusly:

The Effects of Poverty view is that the economic instability, deprivation, risk, stress, and neighborhood effects that accompany poverty best account for why poor students do not perform as well. There is substantial evidence that poor kids, even at the youngest ages, have elevated blood pressure, cortisol levels, epinephrene levels, and norepinephrene levels — all of which are indicators of stress. Poorer children move more often, which has all sorts of negative psychological effects. I could go on, but you get the gist: living in poverty is hard and makes learning more difficult.

The effects of poverty are many, but higher stress features prominently. Researchers have measured the hormonal stress levels of poor and non-poor kids, and found that the former have significantly elevated stress levels. A new NBER study provides more evidence for this “risk-stress” explanatory model. Interestingly, the study does not measure the stress levels of children; instead, it measures the stress levels of pregnant mothers, and then tracks the resulting child to see how they fare.

The short of it is in the abstract: “We find that in-utero exposure to elevated levels of the stress hormone cortisol negatively affects offspring cognition, health and educational attainment.” But there are of course deeper implications. As the paper notes, poverty is associated with higher levels of stress. Putting it together then, we know that the condition of poverty generates more maternal stress, and that maternal stress has damaging effects on children even in the prenatal stage of development.

So, even before birth, wealthier children get a jump on poorer children. The cycle of poverty is much deeper than most imagine, and the pretension that significant economic inequality is compatible with equal opportunity is transparently ridiculous. If you want to help poor kids do better, you make them and their family not poor. There are probably other things you can do on the margins to help them out, but more and more it seems clear that reducing poverty is heads and shoulders above any other program, reform, or policy.

Despite this, advocates of poor children — at least those with prominent platforms — have basically written off poverty reduction altogether. We must assume poverty as necessarily existing, and from that baseline start working out our ideas. That’s garbage, and as this study (among many others like it) have shown: it wont work. Changing distributional institutions so that poor people are less poor is something we can do, and is something we have — at least partially — done before. Studies on the effects of those anti-poverty programs on prenatal health are glowingly positive. Clearly then, we should do more to directly make poor people not poor. There is no reason not to.