Saturday, November 28, 2009

Diane Ravitch -- Wrong on Charter Schools

Diane Ravitch has a new post full of criticisms of charter schools. Unfortunately, the arguments are unsupportable and contradictory.

1. Ravitch has gone to the NAEP website and downloaded snapshots of how students in public charter schools scored compared to students in other public schools. She then concludes, "Overall, public schools continue to outperform charter schools."

No, no, no. You cannot tell anything about how a given type of school is "performing" just by looking at a cross-section of its students' test scores -- without even attempting to take into account the students' backgrounds and previous test scores. And as I point out below, charter school students tend to arrive with somewhat lower test scores than average.

2. Immediately after having praised other public schools for supposedly outperforming charters in student test scores, Ravitch pivots 180 degrees and criticizes charter schools for drawing off the "most successful" students and "disabl[ing]" the public schools!
My beef with charter schools is that most skim the most motivated students out of the poorest communities, and many have disproportionately small numbers of children who need special education or who are English-language learners. The typical charter, operating in this way, increases the burden on the regular public schools, while privileging the lucky few. Continuing on this path will further disable public education in the cities and hand over the most successful students to private entrepreneurs.

It's just not convincing to say with one breath that public schools are "outperform[ing]" and in the next breath that they're being "disable[d]," or to criticize charter schools for serving the "most successful" students just after having claimed that charter students don't score well on national exams.

3. Besides being contradictory, Ravitch's argument is wrong. Charter school students may be "motivated" in some sense, but that certainly doesn't mean that they are all academically successful. Quite the contrary: parents whose children are doing well in the public schools often tend to stay put, while it is precisely the parents whose children are struggling who may tend to seek alternative schools (whether through vouchers or charters). Painting with a broad brush, many charter school and voucher parents have said, "Gee, little Johnny isn't doing so well, maybe I should check into a different school." Such "motivation" doesn't give rise to some sort of huge charter school advantage.

Some evidence for this point: Zimmer et al.'s October 2009 paper analyzing data from locations representing 45% of the charter schools in the nation. They find NO evidence that charter schools are cream-skimming. To the contrary, "in all but one case (Chicago reading scores, which are virtually identical to the district-wide average), students switching to charter schools have prior test scores that are BELOW district-wide or statewide averages."

For another example, take Texas, which is home to over 450 charter campuses, about 10% of all the charter campuses nationwide. In Texas, charter schools that serve predominantly students identified as “at risk” can be rated under an alternative accountability system. In 2007-08, 43.3% of charter schools in Texas qualified to be rated under that system, compared to a mere 3.3% of public school district campuses in Texas (see page 147 here). No doubt, most of the parents of these "at-risk" youth could be described as "motivated" -- motivated to find something, anything, that would help their children learn and stay in school. But this is not obviously an advantage for the charter schools' academic performance.

Incidentally, people often make the same accusation about private schools generally, i.e., that they just skim off all the best students. To the contrary, Derek Neal and Jeffrey Grogger found that “there is evidence of negative selection into Catholic schools. Relative to their public-school counterparts, urban whites who attend these schools appear to possess unmeasured traits that inhibit attainment.” They add this footnote: “Evidence of negative selection is common in this literature. Coleman and Hoffer (1987), Evans and Schwab (1995), and Neal (1997) all report evidence of negative selection into Catholic schools. A common hypothesis concerning this result is that some parents send their children to Catholic schools seeking a remedy for existing problems with discipline and motivation.”



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