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Summer 2018 Leveling the Playing Field in the Game of School Choice
Bob Hammond, Thayer Morrill, and Umut Dur in Nelson Hall

Leveling the Playing Field in the Game of School Choice

Only when Bob Hammond prepared to enroll his child in the very competitive Raleigh, NC-based Wake County Public School System (WCPSS) student assignment process did he notice how it favored sophisticated parents who knew how to game the system.

Hammond, an empirical economist and associate professor in the economics department at the NC State Poole College of Management, had some ideas on how to level the playing field. So he picked up the phone and set up a meeting with the person in charge of student assignment in the Wake County system.

That meeting started an ongoing relationship between WCPSS and Hammond, and two of his Poole College colleagues: Associate Professor Thayer Morrill and Assistant Professor Umut Dur, both of whom are theoretical economists.

“They develop the hypothesis; I go into the data,” Hammond said.

Quantifying Strategic Advantage

As a result of recommendations made to the school system by the three economists, the process of determining which children may attend the most desirable schools no longer gives an advantage to parents who know how to be strategic.

“We used work in economics to advise the school system on alternative assignment processes,” Hammond said. “That was the distillation of work that economists had been doing for 10 years.”

The paper that came out of that initial collaboration, “Identifying the Harm of Manipulable School-Choice Mechanisms,” was published in American Economic Journal: Economic Policy in February 2018.

The research that Hammond, Morrill and Dur conducted provided the first direct measure of the systemic differences in sophistication among students and their success in being assigned to their preferred school.

At the time Hammond’s child was going through the assignment process, WCPSS asked parents and students to rank order their preference for individual schools. The school system factored in its own “priority” criteria, metrics such as whether the student had a sibling already at that school or how the student balanced the school’s socioeconomic makeup.

A subset of more highly desired schools received many more student assignment requests than they could satisfy. In assigning students to a particular school, WCPSS first considered students who had listed that school as their first preference, then seated students based on how high they scored on the WCPSS priority criteria. If any seats remained, only then did WCPSS consider students who had listed that school as their second or third choice.

Some families took a strategic approach by manipulating their true preferences. They listed their top choice as the school at which they had the highest WCPSS priority score, even if they preferred another high-demand school. That way they could be assured of getting into a one of their desired schools, even though it wasn’t their true first choice.

In their study, Hammond, Morrill and Dur referred to these students as “sophisticated students.” Families who listed their true top choice, even if they had very few WCS priority markers, were called “sincere students.”

Parents who didn’t play that strategic incentive potentially were at a disadvantage. If you can reduce the strategic incentive, it levels the playing field.

Many schools across the country conducted their assignment process the way Wake County schools did.

“It was weighted toward sophisticated parents who knew strategic incentives,” Hammond said. “Parents who didn’t play that strategic incentive potentially were at a disadvantage. If you can reduce the strategic incentive, it levels the playing field.”

As theorists, Morrill and Dur study how to design assignment processes. They have experience in matching, one application of which is school choice. The economics literature showed that researchers studying Boston public schools made recommendations for changing the assignment process. The new process turned out to be fairer because it does not require parents to figure out the incentives and concoct a strategy.

Hammond, Morrill and Dur presented new algorithms for WCPSS to use in its assignment process that alleviated the need for parents to strategize.

Ongoing Collaboration

Changing the assignment process “made it so that if A is your favorite school and B is your second-favorite,” Hammond said, “you won’t hurt yourself by putting A first and B second, even if you have a very low chance of getting into A.”

The partnership the researchers established with WCPSS has lasted for some four years. They use data from Wake County to conduct ongoing studies and make new recommendations, for magnet school assignment, for instance. Hammond, Morrill and Dur help WCPSS administer the assignment process and implement their recommendations.

Bob Hammond, Thayer Morrill, and Umut Dur in Nelson Hall
Thayer Morrill, associate professor of economics; Bob Hammond, associate professor of economics; Umut Dur, assistant professor of economics

Each of the ensuing studies starts with a particular hypothesis the researchers are testing and a specific analytical approach.

“Wake County schools share data with us,” Hammond said, “and we, using our analytical tools, study the outcomes of the assignment process, using those data to better understand how alternative assignment processes lead to different outcomes. Using data from the school system, we had a cleaner way to ask questions.”

The old assignment process further disadvantaged students whose parents were not sophisticated by keeping them out of the best schools that could give them a better quality education.

“If your assignment process puts those at-risk students at a further disadvantage,” Hammond said, “you’re making it even harder for them to succeed.”

Reducing the strategic incentives gives everyone access to the same set of opportunities, regardless of how strategic they are in their application.

Using different algorithms is only one way that WCPSS experiments with leveling the playing field. Changing the school system’s priority metrics, reserving seats for the academically gifted, having quotas for certain types of seats are design factors that could make a difference.

“When Wake County Schools contemplates changes,” Hammond said, “we can look in the data to see whether such a change might be good or bad.”

Hammond appreciates how the researchers have facilitated the collaboration between policymakers and economists. The partnership has moved academic insights into practice and improved the school assignment process for parents and students.

“We continue to make recommendations on design changes,” Hammond said. “Reducing the strategic incentives gives everyone access to the same set of opportunities, regardless of how strategic they are in their application.”

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