I don't see "long-term financial success" as being obviously the right metric for judging education at all. It's worth considering, absolutely! But people choose to forego maximum wealth for other priorities all the time, and often for very desirable reasons (both individually and socially). Why shouldn't the metric have something to do with long-term personal fulfillment and happiness? Why shouldn't it have something to do with long-term contributions to society?
I agree with you that the more abundant data (and reduced selection bias) available for schools makes measurements easier for them than for medicine, but I don't think that it's any easier to define an appropriate metric for judging them.
HN really likes to talk money over everything, in spite of how money is merely a means to an end.
I think a better metric would take into account overall health history, years paid into Social Security (as a proxy for income), and food/housing stability. Look at those three factors, and you can get a grip on how a person's life has gone in a way you can compare to others.
I agree with you that the more abundant data (and reduced selection bias) available for schools makes measurements easier for them than for medicine, but I don't think that it's any easier to define an appropriate metric for judging them.