For a bit of clarity...The study has been questioned, as usual, but unless they counted different school systems differently, the results should still be rather valid.
Dropout Prevention Campaign Kicks Off with Stunning New Data | Connect for Kids / Child Advocacy 360 / Youth Policy Action Center
Only about one-half (52 percent) of students in the principal school systems of the 50 largest cities complete high school with a diploma. That rate is well below the national graduation rate of 70 percent, and even falls short of the average for urban districts across the country (60 percent).
In the most extreme cases (Baltimore, Cleveland, Detroit, and Indianapolis), fewer than 35 percent of students graduate with a diploma.

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