There's a simple objective metric that could capture most of what you'd want to know about any school and put USNews's rankings out of business: graduates' achievement. How much are graduates making 10 years later? How many have prestigious jobs or other accomplishments such as research grants or awards? Universities do track these kinds of metrics as part of their alumni fundraising efforts but they're rarely publicly disclosed.
> most of what you'd want to know about any school [...] How much are graduates making 10 years later?
Among my friends in graduate school:
* One was told by their adviser they had enough for a thesis in their second year, and found time to organise a university-wide Dance Dance Revolution championship.
* One was shouted at by their adviser for not coming in to tend to their experiments on Christmas day - the first day they'd taken off that year.
I think a prospective student would like to know which of those experiences they're in store for, regardless of future earnings.
Indeed, if you want to maximise your salary, I'm not sure you should go to graduate school at all...