The original article already provided evidence, based on analysis of the performance of similar students who do and do not get into a selective school. As it says...

"Except that attending those high schools simply doesn’t matter in terms of conventional educational outcomes. When you look at the edge cases – when you restrict your analysis to those students who are among the last let into such schools and those who are among the last left out – you find no statistically meaningful differences between them."

So unless you're calling out the original article, how about offering counter-evidence?

Here you go: http://pricetheory.uchicago.edu/levitt/Papers/CullenJacobLev...

The upshot, attempting to get into a better school is correlated with doing better. Actually getting to go to the school of your choice is not.

Eh, not really. I've learned over the years to avoid providing sources because more often than not the person won't believe you either way and will only use the source as a tangible target for disingenuous attack through motivated misinterpretation. (https://en.wikipedia.org/wiki/Motivated_reasoning)

I typically provide sources in response to replies like: "That's interesting, but I can't really find anything on the matter; can you point me to something?" But if there is no indication that the person actually tried to find corroboration independently I take it as a sign that he is not actually interested in corroboration. I'm sure this is inaccurate sometimes, but it's the best approximation I can come up with.