More on NYC school choice lotteries

 Following my recent post on random numbers in the NYC school choice system(s) for high school and middle school, Amélie Marian writes to me from Rutgers, where she is a professor of computer science and a close observer of school choice.

She writes:

"I just read your blog post about the NYC school lottery system glitch and I found the comparison to plumbing extremely adequate to describe what has been happening with the NYC school admission system these past few years. 

...

"One of the most major recent change is that most admissions are now decided solely by lottery numbers; most schools don't rank students anymore***. The random number, originally designed as a tie-breaker, is now the main deciding factor. With this in mind, I, along with parent advocacy groups, pushed the DOE to provide students with their lottery numbers so that families could adjust their expectations and strategize their lists to avoid being unmatched; in one Manhattan district last year, 18% of students did not receive an offer to a school on their list. I have been working on explaining the system to parents, and on crowdsourcing data to help parents estimate their student's odds of admissions at various schools:

 * Part 1 on the random numbers: https://medium.com/p/bae7148e337d  

* Part 2 on their impacts on strategy: https://medium.com/p/42dd9a98b115

"*** MS admissions is purely lottery-based but geographically limited by district. HS admissions is city-wide. Some HS are allowed to screen students, but the screening is very coarse; this year 63% of students qualify in the top screening group, within the group admissions are decided by lottery numbers.

 "Of course, every modification in the system has had unintended consequences. The "glitch" reported by the NYPost was likely due to the DOE system assigning random numbers to applications and not to students, which was a reasonable approach as long as the numbers were not shared with families. And, as you pointed out in previous blog posts, the addition of waitlists has had repercussions as well. In fact, the DOE has changed the way it processes waitlists yearly since their inception, most likely to fix the problems that the previous iteration created. The latest version unfortunately introduces an incentive to strategize for waitlists in the original choice ranked list. "