Average age of the class at HBS is 27 years. At Columbia, it’s 28. That’s usually the range for most U.S. B-schools: 27-28 years. Some schools, however, don’t provide average age of their class; instead they provide average work experience, which usually is 5 years (to name a few: Wharton, UCLA, and MIT – 5, Stern – 4.5, and Stanford, a relative outlier – 4). The average work experience too points toward a similar average age.
Though the average age of most programs is not too far from 30, B-schools do have some specific concerns about the candidature of applicants falling in 30+ age bracket, though very few air it openly. (There is nothing sacrosanct about 30; it’s just a metaphor for older applicants.)