OP: Although prestige is largely subjective, it is a very real factor for many employers. This is especially true with respect to graduate business (MBA) schools & law schools.
Ranking law schools in three tiers makes sense with respect to employment prospects. The first tier of law schools is recruited nationally, the second tier regionally & the third tier locally.
Very important with respect to graduate business schools.
MBA Schools: The top tier are the M-7. Harvard, Stanford, Penn-Wharton, Northwestern-Kellogg, Chicago, MIT, & Columbia—but, even among the ultra prestigious M-7, Harvard, Stanford & Penn-Wharton are considered to be in a class by themselves.
The next tier is composed of: Duke, UCal-Berkeley & NYU, Michigan & Dartmouth-Tuck.
Yet, with respect to obtaining lucrative employment within 3 months of graduation, the University of Washington-Foster School of Business leads them all with 98% job placement.