For more than two decades, we have heard that charter schools will “save” poor kids from “failing public schools.”

Most comparisons show that charter schools and public schools get about the same test scores if they serve the same demographics. When charter schools exclude English learners and students with severe disabilities and push out students with low test scores, or exclude students with behavioral issues, it is likely to boost their test scores artificially.

Nicole Blalock, who holds a Ph.D. and is a postdoctoral scholar at Arizona State University, compared the performance of charter schools and public schools on NAEP 2013.

She acknowledged the problems inherent in comparing the two sectors. Both are diverse, and demographic controls are not available.

Nonetheless, she identified some states where charter performance is better, and some where public school performance is better.

The result, as you might expect: Mixed.

Bottom line: charters are no panacea.