(Guest Post by Matthew Ladner)
Arizona charter schools continued to display impressive scores and gains on the 2017 NAEP. Note as always that only a random assignment study properly conducted could hope to isolate the role of school quality in all of this, and that such studies are not only unavailable but also are impractical for a statewide system of schools- not all of which are oversubscribed (a precondition for a random assignment study). Thus the role of average school quality in driving the above results remains a holy mystery- likely to be hotly debated, impossible to be resolved in this world. I and others will be digging into Arizona charter subgroup scores in the days ahead.
Now, behold the nothing burger that has been net American academic progress since 2009 (first set of columns). On the math and reading tests 10 points approximately equals a grade level worth of average academic progress (the science exams have a different scaling). Net American progress equals nothing, nothing, next to nothing a tiny bit of something in 8th grade reading.
The middle blue columns are the statewide numbers for Arizona. As you can see they consistently surpass the American nothing-burger. The final set of gains are the gains for Arizona charter school students.
Some of Arizona’s neighbors also have charter sectors that crushed the ball- starting again with Colorado. I’m happy to say that Nevada’s sector made the minimum reporting requirements for NAEP this year, and the results look good. Give me some time to dig, but a monster story may be California charters:
Jay P. Greene's Blog 
Where can I find 2017 NAEP results for charter schools?
Under school factors in the variables: https://www.nationsreportcard.gov/ndecore/landing