Bizzolt writes:

DC Public Schools HS teacher here (although I'm not returning next year, as is the case with many of my colleagues). As noted, one of the biggest factors in the graduation rates is the unexcused absences–if you look at the results of our external audit and investigation here, you see that for many schools, a significant number of our seniors "Passed Despite Excessive Absences in Regular Instruction Courses Required for Graduation"–over 40% of 2017 graduates at my high school, for example.

So the attendance policy is being strictly enforced now, and you can see how from that alone, a ~30% drop in expected graduates is possible. Some more details about strictly enforcing the attendance policy though:

1: DCPS has what's called the '80 20′ rule: A student that is absent for at least 20% of their classes is considered absent for the whole day. 2: Most schools have 5 periods, so an absence in one class would be considered an absence for the whole day. 3: If you have 10 or more unexcused absences in a class, you automatically get an F for the term. 4: If you are over 15 minutes late for a class, that is considered an unexcused absence. 5: A majority of these absences are in first period. 6: A majority of students in my school and many others live in single parent households. 7: These students are typically responsible for making sure their younger siblings get to school, if they have any. 8: Elementary and middle schools in my neighborhood start at the exact same time as high school. 9: Their doors do not open until 5 to 10 minutes before the starting bell, presumably for safety reasons. 10: Refer to point 4.

There's many other problems at DCPS to be sure, but this set of circumstances alone is causing the largest increase in failing grades and graduation ineligibility at my high school, and basically every other 90+% black school in the district. You could see how this accounts for quite a bit of the difference between white and black graduation rates as well. There's a reason why across the board, DCPS schools were not strictly enforcing this policy in previous years.

It looks like most other school districts don't have this policy; it seems plausible that this is the main difference between DC and other poor school districts that nevertheless manage to pass most of their kids.

Userfriendlyyy also focuses on the absences:

Looks to me like the policy they changed was losing credit for bad attendance. This might be from a few things. Kids might need to help out with the family finances. The only part of the job market that is doing well right now is low end unskilled workers who are willing to get paid crap (no matter how much the financial press wants to pretend otherwise, I listened to an hour of local NPR and the Topic was 'call in and tell us how the booming job market is helping you out', 20 callers not one had anything good to say and my state has one of the lowest unemployment rates in the country). If you know you don't have the grades for a scholarship, your family is broke and since we have effectively made going to college impossible for anyone but the offspring of the oligarchy, and you can find a minimum wage job easily; what exactly is the utility of that little piece of paper compared to the ability to put food on the table tonight?