You want to improve your basketball game. Would you rather practice one-on-one with your older brother, who’s on the JV team, or with Kobe Bryant?
Unless you possess a serious streak of masochism, you did not choose Kobe Bryant — for reasons that should be obvious: while you will definitely improve playing with someone marginally better than yourself, you will accomplish nothing by playing with someone exponentially better than you are. Except, in all likelihood, the rapid deflation of your self-esteem.
Applying this principle more broadly, it’s easy to see how associating with peers slightly better than ourselves — whether academically, professionally, or morally — will push us to higher levels in our own conduct and performance. But the benefits of implied social pressure disappear when we perceive our peer group to be functioning on a higher level than it actually is.