Friday, September 5, 2014

Selection effects on steroids

UPDATE: I just put out a collection of our early posts on education (Things I Saw at the Counter-Reformation).  The impact of attrition is one of the big running themes in the book.


I'm about to have a lot more to say about the various ways high attrition can pump up a school's performance metrics, some directly through removing low performers, some indirectly through peer effects, treatment interactions and accounting tricks. At the risk of spoiling the punchline of those future posts, it is next to impossible to perform meaningful analyses of the academic quality of high-attrition schools. About the only safe conclusion is that those schools are worse than they look.

If charter schools are going to have a future (and I hope that they will, though my reasons will have to wait for another post), they will have to overcome two existential threats, both of which originated not with their critics but with their supporters. It was supporters who pushed a radical deregulation agenda that led to massive looting of the system and it was supporters who advocated for a flawed system where success was defined solely by metrics and those metrics were easily cooked by methods which took a brutal toll on kids.

In a devastating post, Diane Ravitch spells out just how bad the problem has gotten.
Reformers tend to make two very different arguments about charter schools. Argument #1 is that charter schools serve the same students as public schools and manage to put public schools to shame by producing amazingly better results on standardized exams. Therefore, reformers claim, if only public schools did what charter schools do (or better yet, if all public schools were closed and charter schools took over), student learning would dramatically increase and America might even beat South Korea or Finland on international standardized tests. When it is pointed out that, as a whole, charters do no better than public schools on standardized tests [2], reformers will quickly turn their attention to specific charter chains that, they claim, do indeed produce much better standardized test results. So what’s the deal with these chains? Well, in every case that has been subjected to scrutiny their results are extremely suspicious. Here is a short list of examples:

1. Achievement First in New Haven had a freshman class of 64 students (2 students enrolled later), and only 25 graduated- a 38% graduation rate- yet the school claimed a 100% graduation rate by ignoring the 62% attrition rate. [3]

2. Denver School of Science and Technology (DSST) had a freshman class of 144 students and only 89 12th graders- a 62% graduation rate- yet the school (and Arne Duncan) claimed a 100% graduation rate by ignoring the 38% attrition rate. [4] As a 6-12 charter chain, DSST also manages to attrite vast numbers of their middle school students before they even enter the high school.

3. Uncommon Schools in Newark disappears 38% of its general test takers from 6th to 8th grade.[5] Another analysis found that through high school the attrition rate was, alarmingly, much higher “Uncommon loses 62 to 69% of all males and up to 74% of Black males.”[6]

4. BASIS in Arizona- “At…BASIS charter school in Tucson, the class of 2012 had 97 students when they were 6th graders. By the time those students were seniors, their numbers had dwindled to 33, a drop of 66%. At BASIS Scottsdale…its class of 2012 fell from 53 in the 6th grade to 19 in its senior year, a drop of 64%.” [7]

5. The Noble Network in Chicago- “Every year, the graduating class of Noble Charter schools matriculates with around 30 percent fewer students than they started with in their freshman year.” [8]

6. Harmony Charters in Texas- “Strikingly, Harmony lost more than 40% of 6th grade students over a two-year time.” [9]

7. KIPP in San Francisco- “A 2008 study of the (then-existing) Bay Area KIPP schools by SRI International showed a 60% attrition rate…the students who left were overwhelmingly the lower achievers.” [10]

8. KIPP in Tennessee had 18% attrition in a single year! “In fact, the only schools that have net losses of 10 to 33 percent are charter schools.” [11]

In every case these charter chains accepted students that were significantly more advantaged than the typical student in the district, and then the charters attrited a significant chunk of those students.

Success Academy in New York City plays the same game. It accepts many fewer high needs special education students, English Language Learners, and poor students. [12] It attrites up to 1/3 of its students before they even get to testing grades and then loses students at an even faster pace. It selectively attrites those students most likely to get low scores on standardized tests. [13] It is legally permitted to mark its own exams (as are all New York City charter schools) while public schools cannot. It loses 74% of its teachers in a single year at some of its schools. [14] The author of the Daily News editorial that sparked the initial blog commented “even in the aggregate that wouldn’t seem to account for” the results. It is entirely unclear what he means by “in the aggregate.” But it is clear that he has his arithmetic wrong. A charter chain that starts with an entering class that is likely to score well on standardized tests, then selectively prunes 50% or more of the students who don’t score well on standardized tests and refuses to replace the disappeared students with others, can easily show good standardized test results with the remaining students. Any school could do this. It’s really not rocket science.

And here are the footnotes

[5] /
[13] The high attrition rate before testing in 3rd grade may explain the data pattern noted in this analysis.

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