I didn't skip it. I read it (and I've read similar studies in the past.) I'm not saying the data is wrong, I'm saying the conclusions you're drawing from it are nonsensical.
The study is saying that students who are held back are less likely to graduate than students who are just passed along regardless. Another way of interpreting that is to say: in any group of people who are held to a standard, some are bound not to meet that standard.
I've worked in two school districts where grades are regularly adjusted and students are matriculated without basic reading/writing/math skills. From what I've heard from colleagues, this is standard practice across the board in public schools. Administration does this to keep up appearances and keep the graduation rate up so that alarms aren't sounded at the state level and they can keep their jobs. When a student is passed along when they shouldn't be, it begins a slippery slide to the finish where each subsequent teacher finds it harder and harder to broach the subject and each administrator finds it a more daunting task to actually address the problem. When a student is shunted along once, it's game over for that kid in terms of receiving attention and support. Yeah, the teachers and IAs should help... but how can they help these 4 or 5 students without neglecting their 130 other students?? Not to mention the biggest problem of all: the students who are shunted along from grade to grade are being taught that they don't have to do anything to succeed and promotions will just be handed to them. This means that when I actually try to help them and get them to do something, they are unwilling to work at all. Like nothing. Nada. And can you blame them?
Yeah, I don't think that all students should graduate high school. I think that it should be possible to fail out of school if you don't do any work. I think that it's wrong to dilute the education of the rest of the kids so that, despite their best efforts, a few extra kids can be dragged across the stage and be handed a diploma. I'm willing to fail that <1% of kids so that the 99.9% can have a better education.