The Louisiana Voucher Accountability Sweepstakes

The situation with vouchers in Louisiana is obviously quite complicated, and there are strong opinions on both sides of the issue, but I’d like to comment quickly on the new “accountability” provision. It's a great example of how, too often, people focus on the concept of accountability and ignore how it is actually implemented in policy.

Quick and dirty background: Louisiana will be allowing students to receive vouchers (tuition to attend private schools) if their public schools are sufficiently low-performing, according to their "school performance score" (SPS). As discussed here, the SPS is based primarily on how highly students score, rather than whether they’re making progress, and thus tells you relatively little about the actual effectiveness of schools per se. For instance, the vouchers will be awarded mostly to schools serving larger proportions of disadvantaged students, even if many of those schools are compelling large gains (though such progress cannot be assessed adequately using year-to-year changes in the SPS, which, due in part to its reliance on cross-sectional proficiency rates, are extremely volatile).

Now, here's where things get really messy: In an attempt to demonstrate that they are holding the voucher-accepting private schools accountable, Louisiana officials have decided that they will make these private schools ineligible for the program if their performance is too low (after at least two years of participation in the program). That might be a good idea if the state measured school performance in a defensible manner. It doesn't.

Louisiana's "School Performance Score" Doesn't Measure School Performance

Louisiana’s "School Performance Score" (SPS) is the state’s primary accountability measure, and it determines whether schools are subject to high-stakes decisions, most notably state takeover. For elementary and middle schools, 90 percent of the SPS is based on testing outcomes. For secondary schools, it is 70 percent (and 30 percent graduation rates).*

The SPS is largely calculated using absolute performance measures – specifically, the proportion of students falling into the state’s cutpoint-based categories (e.g., advanced, mastery, basic, etc.). This means that it is mostly measuring student performance, rather than school performance. That is, insofar as the SPS only tells you how high students score on the test, rather than how much they have improved, schools serving more advantaged populations will tend to do better (since their students tend to perform well when they entered the school) while those in impoverished neighborhoods will tend to do worse (even those whose students have made the largest testing gains).

One rough way to assess this bias is to check the association between SPS and student characteristics, such as poverty. So let’s take a quick look.