Cream-skimming is not driving charters' success in New York City

Charter school critics often argue that public schools of choice post high standardized test scores largely because they enroll only a select group of students who know to apply to them. A new comparison, however, finds that charters compete with, and, in some ways, surpass New York’s selective public schools, showing the achievements of charters are not so easy to dismiss.

Charters have no control over who enrolls in their schools; anyone can apply. When more students apply than there are available seats, enrollment is granted randomly. It is true that those who apply might be more advantaged than others in the neighborhood – after all, their parents had the necessary informational resources to know how to apply and that they wanted to do so – but charters can’t weed out undesirable applicants directly. And many students apply to charters specifically because they are having trouble in traditional public schools.

Meanwhile, the common claim that traditional public schools are open to all is simply wrong. Traditional public schools aren’t open to all students, they are open to all students who live in a particular geographic zone: only the select group of those who can afford to live in Beverly Hills can go to Beverly Hills High.

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Some public schools go further and explicitly select among a group of applicants based on characteristics related to their academic promise and behavior. Perhaps the most prominent example of these selective public schools is New York City’s elite high schools such as Stuyvesant and Bronx Science, where students are enrolled based on an admission test. But less often discussed are the city’s 98 traditional public middle schools that use some sort of screening process to admit students. According to information on the district directories, these schools consider at least one of several criteria to directly select applicants for admission. The criteria range from consideration of the student’s standardized test scores, their report card or attendance rate. Several schools require students to sit for an interview.

Those who would argue that charters post high test scores only because they cream-skim for students must grapple with the fact that charters perform as well as or better than traditional public schools that explicitly and unapologetically cream-skim for students.

The mere existence of these selective traditional public schools should be enough to embarrass those who argue that charters aren’t public schools because their students choose to enroll in them. In a new report for the Manhattan Institute, I go a step further and compare the average performance of charter schools to that of selective and unselective traditional public schools in the city. The former comparison, of course, puts charters to a hard test given that they select applicants randomly while the selective traditional public schools get to pick among their applicants.

Without making any adjustments for the characteristics of their students, the city’s charters perform as well as the selective schools in math and only slightly worse in ELA. Charters perform just as well in ELA and substantially better in math when we adjust for the fact that their students are, on average, more disadvantaged than those in the selective middle schools. Results are similar for both the percentage of students scoring at or above the proficient level and on a measure of test score growth. Both charter and selective traditional public schools post higher scores than regular traditional public schools in the city, on average, when accounting for student characteristics.

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The observational analysis in my report shouldn’t be interpreted as showing that students benefit from attending a charter instead of a selective or other traditional public school (Though, prior research capable of making such claims has found exactly that). Nor am I arguing that it’s inappropriate for the city to operate selective middle or high schools. A city as large and diverse as New York should offer a wide range of schooling options.

What my analysis implies is that the city’s charter schools don’t post high test scores simply because of which students they enroll. Those who would argue that charters post high test scores only because they cream-skim for students must grapple with the fact that charters perform as well as or better than traditional public schools that explicitly and unapologetically cream-skim for students.

Marcus Winters is an associate professor at Boston University, senior fellow at the Manhattan Institute and author of the new report, “New York Charter Schools Outperform Traditional Selective Public Schools.”