One problem is that Small-fish-in-big-pond-effect, a good chunk of us realized there that we weren't special anymore, there wasn't the honor and praise for being top- and consequently that drive was lost.

Plus, once some schools become well established and start to attract highly talented kids- kind of kids who can do well by themselves without much external help, the school itself, I mean teachers and administrators, doesn't have to be very good. Their success starts to depend more on their ability to attract talent, and less on actually nurturing and developing them. Past success bring more success- a sort of virtuous cycle.