(Guest Post by Matthew Ladner)
The Arizona Charter School Association analyzed public school migration patterns for 85,000 kids who switched among public schools by their prior AZMerit scores. And well this is what it looks like:
So kids transferring from Arizona districts to Arizona charters have below average AZMerit scores. Those transferring from charters to districts have above average AZMerit scores. This is to put things mildly not consistent with the litany against charters that claims that Arizona charters are engaging in massive creaming of students. If anything, this data suggests the opposite: that if there is creaming occurring, it seems to be in the direction of districts creaming charters.
Mind you the creaming thesis already had huge problems, the first of which being math. When you see scores improving in both district and charter schools, it makes it very difficult indeed to argue that charters have circumvented lottery requirements (which districts don’t have) to only get the high flying academic kids. If this were the case it would have been a really neat trick to see Arizona districts showing better gains than the national average despite some of the nation’s largest Great Recession funding cuts, despite a continuing trend into deeper majority-minority states and despite losing tens of thousands of their top performing students.
The average transfer from district to charter having below average scores in fact might in part explain the district gains we see, but then you get back to those charter gains…looks like they are having a lot of success getting kids who were off track back on it.
I would be very interested to see the average grade level by transfer group in this data. My guess would be the average district to charter transfer student is an elementary student, and that the average charter to district student is more of a middle school student. In any case, when you are taking in lower than average kids and sending back higher than average performing kids as a sector, this myth is…
Jay P. Greene's Blog 
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Question – Regarding The AZ Merits Test Scores used in this analysis. Were the scores a composite of Academic Year 2015 and 2016, or the 2016 performance?
The most meaningful analysis would be a comparison of the change in performance from 2015 to 2016 for those who migrated in each direction between Public and Charter schools.
Footnote – while this is great stuff, it needs to be taken down to the micro level to make sense. As for SUSD, the mass migration to Charters was 2,200 White Higher Income kids from the 85255 zip code and Ancala area to White Higher Income region domiciled Charters. That move started in 2011 and continued through 2018. The Ten Year enrollment data by grade, by school, and by demographics is a really interesting report.
Would love to share it with you when it’s final edit comes out. A team’s been testing the data for the last couple of weeks preparing for its release. Then plotting the growth/shrinkage in enrollment by the emergence of each new Charter or expansion of each older Charter in the District.
If we can somehow capture AZ Merits scores for each transferring student – each direction – then we’re getting to some really meaningful stuff.
Mike-
There may not be much other than higher income White kids in 85255, and as of 2012 there were 9,000 kids who lived in SUSD but did not go to school in SUSD. It is probably more than 9,000 now, but I’m happy to look at whatever data you produce.
I also agree that this data deserves further examination, which I am confident will occur.