Several studies show that a combination of market pressures and state or authorizer policies help prevent public charter schools from “cream-skimming”—enrolling high-achieving, less-challenging, or less-costly-to-educate students—and shunning or forcing out low-achieving, more-challenging, and more-costly-to-educate students. The extent to which these practices may occur in private school choice programs, however, is less understood, as most states generally allow private schools to follow their own admissions and retention criteria. In an effort to shed some light on the matter, a recent report from Joseph Waddington, Ron Zimmer, and Mark Berends examines the data from private schools participating in Indiana’s statewide voucher program.
Analysts use eight years of data (2010–11 through 2017–18) from the Indiana Department of Education, which includes information on students attending district, charter, magnet, and private schools (including voucher and non-voucher students). Critical to the study design, almost all students in Indiana must participate in statewide testing, including private schools that take part in the voucher program. Analysts focus on the students who switched schools between school years and distinguish between structural moves (meaning that students are moving into schools with higher grade levels) and non-structural moves (meaning they switched schools for any other reason). Their primary outcomes are math and English language arts achievement and potential differences in the creaming/pushout status of students with special needs (SPED) and those learning English (English language learners/ELL), since those needs are generally costlier to address.
For the pushout analysis, the scholars examine whether students made a non-structural move. They want to see whether low-achieving or costlier-to-educate voucher-receiving private school students are more likely to transfer out of a private school and into a district school compared to similar students who are voucher-eligible (but not voucher-using) and make a non-structural move from their traditional public school. The primary question is whether students have below average achievement in math and ELA relative to peers in their school each year.
For the cream-skim analysis, they examine whether students made either a structural or non-structural move between years, since there could be motivation to “cream” a student regardless of whether they reached the terminal grade of their previous school. They look at whether a student has above-average achievement—again relative to their peers in their school each year—and no discipline issues (the analysts have suspension/expulsion data only from the public schools). They are examining the difference in the relative likelihood of making a move for a high-achieving/less-disruptive/less-costly-to-educate student who receives a voucher to attend a private school, compared to those same types of voucher-eligible students who make a move without a voucher.
Analysts find no evidence that private schools are cream-skimming higher-performing, less-disruptive, or less-costly-to-educate students from district schools. They also do not find strong evidence that pushout occurs relative to English language learners and students with special needs. However, they do find evidence consistent with the claim that the lowest-achieving voucher students are being pushed out of private schools at a modestly higher rate than their similarly low-achieving, voucher-eligible traditional public school peers (1 to 3 percentage points higher)—as well as their higher-achieving voucher-using private school peers (3 to 9 percentage points higher).
Note that this is a descriptive—not causal—study. Which means that the so-called “pushout” data could also be consistent with any number of voluntary student departure scenarios, such as that private school is too hard (or too easy) for students; that voucher students are having trouble making friends or otherwise fitting in; or that the commute from home to school is too long. We need more information to determine the mechanisms behind the observed outcomes. Still, the lack of obvious cream-skimming and minimal pushout are both encouraging findings, seeing that private school choice programs have far fewer mandated guardrails to prevent them from occurring.
SOURCE: Joseph Waddington, Ron Zimmer, and Mark Berends, “Cream Skimming and Pushout of Students Participating in a Statewide Private School Voucher Program,” Annenberg Institute at Brown University (August 2022).