It don't believe that's how it works. Here's another question to demonstrate this: How did the University of Michigan become a prestigious public university? In part, by accepting all the bright Jewish students that Harvard blocked from admission because of racial quotas. The subsequent success and honors of their alumni built up their reputation and donor base to what it is today. So aside from this argument being unfalsifiable and circular itself (those who went to Harvard would've been successful if they didn't go to Harvard, but they went to Harvard...), we would have to accept that all the Jewish students rejected from Harvard we're just never going to be successful anyway, which the historical example invalidates.

... In other words they were successful despite not going to Harvard!

I didn't say it was a good system; just observed that it is how it is.