There is a good "This American Life" episode that touches on this argument somewhat. Due to mismanagement and zoning issues, students at a low-income and underperforming public school in Missouri were forced to go to a wealthier and better performing school a few towns over. The daughter of a family profiled for this episode demonstrated significant gains in her grades, vocabulary and social life. She isn't alone; there is data that supports that "integrating" students like this improves performance in kids that would typically underperform at a less accomplished school alone.

My fiancée, a HS math teacher for eight years, saw this in her classes too. The smarter kids (the kids that got the material quicker) would catch up the kids that were lagging behind. While she did have to prepare more nuanced lesson plans, she did see improvement in kids with similar characteristics of classically-underperforming kids she taught previously.

Given this, I think smart schools do humanity a great disservice.