Of course Bryan favors rising wealth and falling fixed costs, as do I. But in the meantime he also should admit that a) education “parachuted” in from outside can have a high marginal return, b) collectively stronger pro-education norms raise demand and can alleviate the high fixed costs problem, c) there are big external benefits, some operating through the education channel, to lowering the fixed costs, d) stronger pro-education norms put a region closer to a “big breakthrough” and weaker education norms do the opposite, and e) a-d still impliy “too little education” is the correct judgment. On b), some evangelical groups in Latin America do seem to have stronger pro-education norms in their converts and it appears to be much better for the children of these families and no I’m not going to buy any response which ascribes the whole effect to selection.
Signaling models are important but they are not the only effect and of course a lot of signaling is welfare-improving for reasons of screening and sorting and character reenforcement. The traditional story of high social returns to education is supported by evidence from a wide variety of different fields and methods, including cross-sectional growth models, labor economics, political science, public opinion research, anthropology, education research, and much more. You can knock some of this down by stressing the endogeneity of education, but at the end of the day the pile of evidence, and the diversity of its directions, is simply too overwhelming.