In free markets (i.e., no zombies), companies evaluate how well they invest capital by measuring profitability. The military measures readiness, i.e., how capable the people, equipment, tactics, etc. are of executing the mission. Fiat education measures grades, test scores and, above all else, spending. If we applied first-principled thinking to education, what should we be measuring? 
Discussion
LTV - lifetime value.
Everything measurable is always just a neverending optimization for the life time value of the given service (product).
Profit generated by a student after finishing the school might be the proxy I go with.
But also, whenever you centralize all efforts and align incentivee around a single proxy metric, people start gaming it, and the metric looses its proxy value. The system also gets very fragile if everyone shoots for the same proxy. We should let the individual customers (students, families, communities) to subjectivily define what they see as their LTV definition.
So maybe, if you wouldn't have the centralized power of the public educatiin in the first place, you wouldn't have to argue with people about the best measurement of its quality ✌️