Though my DVR has yet to record HBO's documentary, Hard Times at Douglass High, that's not going to stop me from opining anyway.
Douglass High's primary problem is that most of its students do not possess the skills needed to access a high school curriculum. Most of the students don't belong at Douglass High or any high school for that matter. Most of the them belong in remedial classes teaching elementary school material. This, of course, assumes that the students are still willing to sit in a classroom attempting to learn after experiencing nine years of academic failure. I doubt many of them are. I suspect many of them are causing serious disruptions to whatever classrooms they happen to be in.
Douglass High's problem is social promotion. The elementary and middle schools that feed into Douglass High failed to properly educate their students and passed the buck right on to Douglass High. Douglass was handed a thankless job.
Douglass High is the end point for a very broken educational system. Even if Douglass High were capable of remediating its students at a high rate, the results would still likely not show up in any state test.
Douglass High's primary problems lie elsewhere.