On the other hand, this
http://www.detroitnews.com/story/new...ains/81820844/ says Detroit schools have really increased graduation rates. The article doesn't speculate as to why/how, although the highest rates are at specialized schools, with focused curriculum. I would think tapping off all of those students would have a "pulling down" effect on the neighborhood schools they left, but maybe not.
On the other other hand, I look at all Detroit stats with a jaundiced eye.
