Very good post! I'm similarly skeptical of the "education at all costs" craziness that seems to pass for policy around the world. Education clearly has benefits and clearly has costs, not all education is created equal, and every circumstance and environment is different.
The only way to learn what kind of rational expectations equilibrium would exist in education is for all forcing functions and compulsory subsidies to be removed, then see how people arrange their investments in education. Trial-and-error + skin in the game would surely tend towards a more realistic equilibrium investment rate than edicts from up high.